ok let me explain better, maybe this time i'll make sense
a galaxy is eligbale to receive new players if it is in the bottom 25% by number of planets. It does not matter how many spaces it has, it is equaly likely to get a new planet as any other galaxy in the bottom 25%.
a galaxy canot exile people if it is in the bottom 15% - if it is in the bottom 15% is is allready eligible to get new planets, so there is no purpose in further exiles.
This does a number of things - forces carful thought about exiling, so galaxies think about who they want to exile, at the same time it means people who have just signed up get a bit more time to proove they may actualy become decent active players.