What counts, how to work out your total, the order to pray them in, and the three times of day when qaza cannot be prayed at all.
No qaza prayer is offered during these three windows. Wait until the window has passed, then pray.
The teal is the day as it is open to you. The three brass sections are the only parts that are closed, and together they come to under an hour.
From the moment the sun begins to appear until roughly twenty minutes after sunrise. If sunrise on your timetable is 06:30, wait until about 06:50.
Roughly ten to fifteen minutes before true midday until the sun has clearly passed its highest point, which is when Dhuhr begins. If Dhuhr starts at 13:05, stop by about 12:50 and resume once Dhuhr has come in.
The last twenty minutes before sunset, while the sun turns pale and can be looked at directly, until it has fully gone down and Maghrib has come in.
Taken together that is around fifty minutes out of the day. Every other minute is open to you, including through the night.
Sunrise, zawaal and sunset shift through the year, so take the times from your local timetable or prayer app rather than fixing them. The allowance for praying the current day's own Asr during the sunset window does not extend to qaza prayers.
Qaza e umri is making up a lifetime, or a large number, of missed obligatory prayers. Counting runs from the point prayers became compulsory for you, which is the age of puberty.
Make the intention for the earliest missed prayer of that type, for example the first Fajr I missed. As each one is completed the next earliest becomes the target, so you work forward in order without having to track individual dates.
The steady approach is to pray one qaza alongside each daily fardh prayer, so a qaza Fajr before or after your daily Fajr. That clears the backlog without overloading you. If you want to finish sooner, set aside extra time each day and let the app show you the daily figure you need to hit.
Consistency beats intensity. A pace you can hold for years will clear more than a heavy week followed by nothing.
A traveller shortens Dhuhr, Asr and Isha to two rakats instead of four. Fajr is two in any case, Maghrib stays three, and Witr is not shortened.
A prayer follows the state you were in when you missed it, not the state you are in when you make it up.
So a prayer missed on a journey is made up shortened, however long afterwards you pray it. Being at home when you make it up does not change it back to four. The opposite holds too: a prayer missed at home is made up in full even if you are travelling when you repay it.
That is why the app keeps them apart. Every prayer you missed on a journey goes on its own travel record, Fajr and Maghrib and Witr included, and the app tells you which of them are made up shortened and which in full. Your overall total does not change. A missed prayer is a missed prayer either way.
The dark marks are prayed in full. The brass marks are the ones prayed shortened, and they stay shortened however far down the road you make them up.
If you are unsure whether a particular journey counted as travel, or how far you must go for it to count, ask someone qualified in your local tradition rather than guessing.
Each entry is counted as whole days from the start date to the end date, including both. Every prayer set to that period is counted once for each of those days, and leap years are included.
Adding the same prayer twice over overlapping dates will count it twice, so keep your entries separate. If a figure needs correcting, use the manual adjustment rather than reworking the dates.
The app counts more than prayers. Qaza roza, the fasts of Ramadan you did not keep, are entered a Ramadan at a time by the year you remember, with the number of days you missed of it. The Ramadans are counted on the Islamic calendar, which matters because Ramadan moves about eleven days earlier each year: a span of fifteen ordinary years contains seventeen Ramadans, not fifteen.
Fidya is a separate obligation and is left to you. Every missed fast is counted here with no deduction and no reason asked for.
Missed sajdah tilawat are counted too. Fourteen fall in a complete recitation of the Quran, so completions are the usual way in. Because a sajdah becomes due on hearing one of those verses as well as reciting it, the figure from completions is a floor rather than a total, and you can raise it by whatever you judge to be right at any time.
None of the four is ever added to another. Qaza namaz, qasr qaza namaz, qaza roza and sajdah tilawat each have their own total and are each recorded as done on their own.
This app is a counting and tracking tool, not a religious authority. On any question of ruling that applies to your own case, ask a qualified scholar.
The app does the arithmetic. You give it the years, it gives you the number.
These pages explain what Qaza Tracker is. The counting, the recording and your own figures all live in the app, which opens once you log in and stays open until you sign out.