Thank you guys, someone just explained me it last night and now I get the logics behind it. So I will leave in here an easy way of understanding the logics behind it as well as where I was mixing things up.

Basically I was thinking “How can I know which team will I be if I dont know how many people we are in total?”. The division I was doing was, if for example we have 100 people, we divide them 100 by 4 and the first 25 people will go into group 1, the next 25 (from 26 until 50) into group 2, the next 25 (from 26 til 75) into group 3 and the remaining people into group 4.

The explanation I was given is that this calcultion should be based on logics, and always the most effective way of doing things is also the most simple of it. The way I was doing it needed an extra answer (total number of people) but the optimal way of doing it would be for example when in physical education class the teacher divides the students into teams. So let’s say 10 kids divided into 3 teams. The teacher wouldnt divide 10 by 3, many times he wouldn’t even need to count the total number of kids. He would simply say: “You go into team number one, now you, the next in line, go into team number 2, next one into team number 3, now you again into team number 1, next into team number 2, next one into team number 3, now you again into team number 1, next one into team number 2 and next one into team number 3… wait, that’s 9 kids but there is one child remaining, so you go into team number 1”.

So again, the most effective way of doing something is usually the simple way, and by having to ask extra questions to be able to solve the problem you are already adding a degree of complication to it.