It’s simply a guide to tell you which security to use.

3 men on each means both north and south are equally busy so don’t do out of your way to use the alternative. This could mean no people waiting at all in both or both are rammed with 15 min queues.

2 on one and 5 on the other means use the alternative as you are likely to have a shorter wait. The people are in no way representative of the amount of people waiting in security, just a comparison of the two.