They do a weird conversion in my experience. I think for the first “minute” it just counts all numbers in the seconds field as seconds, then as it counts down, the next minute is only 60 seconds.

Eg I think I’ve tried putting in 90 seconds, and that is actually 90 seconds, same as if I were to put in 1:30 (minute and a half)

So I might guess something like 4:90 == 5:30