No it's more like this: humble takes a 30% fee, then for the remaining 70% the user can decide how to divide in three parts.
So on this specific example, all of the three sliders go from 0 to 55.71, with humble that takes 23.88 in addition to the selected percentage.
So, if the user decides to give 33,3% to each one, the dev takes 18.71, the charity takes 18.71 and humble takes 18.71+23.88 fee
The sliders are purposely deceiving to pretend they are not taking the biggest slice of the pie