At the moment the feature does NOT require rest packs depending on the number of affected players but depending on the number of signed players.
[IMG]

[/IMG]
Though the affected players are 18, the feature requires 7 packs which is the total number of players divided by 3.
Though the number of affected players is 14 at most (don't know if players with 95-98% resting will be affected), the feature requires 8 packs which is (number of signed players) 22/3=7.33 rounded to 8 packs.
So at the moment the feature is a waste of packs unless ALL of your players are going to be affected AND the number of your players is a multiple of 3 (otherwise you lose a pack by the rounding up of the result of the division).