or if i leave it blank will it take the 15 points and split it with say 26 people now since i have the box checked for someone in the waiting list.
That is what it would do, currently. You can specify an override value for those, but entering "50%" as the value won't do anything useful there.
If you're going to redistribute, though, I'd recommend either giving full distribution to everyone, or switch to static boss values. Mixing redisitrubion with static override amounts can be both tedious for you, and will definitely mess with your averages.
The only alternative, in this situation, is to do the math manually: Take the total points spent, and set the amounts accordingly with your custom formula.