GPA is calculated to 2 decimal places, in the range [0,4]

However clearly a 2.XX will not get you into POST, so lets only consider the range [3,4]

This gives 10^2 + 1= 101 possible GPA values. They are only planning to admit ~200 students, so in the best case there are 400/101 = ~4 students for each GPA value.

If they admit starting from the highest GPA, then they will admit at best the 200/4 = 50 highest GPA values. Since 4 divides 200, no 2 students will have the same GPA but different POST results.

At worst all students achieve the same GPA, in which case at least 200 students will be rejected only because of the cap.

I guess [0, 200] students will be really unlucky. Since both the extreme scenarios are highly unlikely and pretty much impossible, it means the range is more like (0,200+)