What does this tight...10 to 12 repetitions and work up to two sets of 12 to 15?

What does this tight...10 to 12 repetitions and work up to two sets of 12 to 15?
It means do the exercise 10-12 times at first next work up to doing the exercise 12-15 times, rest for a minute, then do the exercise again 12-15 times.
it penny-pinching that each set is equal to 12-15 pushes or lift so every time you start you do a set of 12-15 stop then do another set of 12-15 hope that help