The trick to understand frequentist approach here is, it doesn't matter what number the tanks have other than the one with max number. 1 2 3 60 is same as 57 58 59 60 ( like it doesn't change the probability to win lottery with ticket 000001 or 639465 )
So the knowledge is only you have 4 tanks with max ID=60.
That's a large part of it, the other half is picking N numbers from a range 0-100% what is the reasonable minimum and maximum percentile for the largest number. Next, what happens when you keep adding new numbers to chose from over time.
