If you're going to go in with "What part of all this don't some of you get?", you'd best not miss. You missed. (at least, you weren't totally right
)
Firstly, that is assuming that your first tier cap is not just filled with players, but maxed out in $$ too - a possibility, but not a certainty. The number added in is based on game/weekly payment for that week and not their total salary. Most 2nd tier guys will be fairly low so if there is any space (and there clearly is, given certain other players playing games - Satae, Bell, Papalii etc) they won't be taking up too much room.
Secondly - and more importantly - it doesn't actually apply this week. Why? Because neither team can make the finals. NRL been giving these exemptions for 2-3 years now.