Four ways to divide one total
Equally is the default. By share gives one person two shares and another a half. By percentage lets you set 40/30/30 and warns you when it does not add to a hundred. Fixed plus the rest lets one person put in a set amount while everybody else splits what is left.
None of these is labelled the fair one. Fairness is the group’s call; the job here is to get the arithmetic right whichever they pick.