It's going to represent the number of seconds, so the possible range is 00 to 59.
one way is like the below. There may be a better method but this is the way i would use it.
DECLARE @seconds INT = 5
DECLARE @Stringlength INT = 2
SELECT REPLACE(STR(@seconds,@Stringlength),' ','0')
-- output = 05
If you put anything greater than 9 it won't pad it with a 0 infront (e.g. 10 will be 10)