When you use DistroKid, you keep 100% of your earnings, minus banking fees/applicable taxes.
We feel strongly that you shouldn't give a percentage of your earnings for streams / sales to your distributor. You earned the money, not them.
The only time we take a percentage, is if you opt into our optional "YouTube Content ID" service. That's the service where we find videos on YouTube that use your music-- and tell YouTube to monetize them (more info here). We keep 20% of the revenue from YouTube videos that we find, and send you the rest (80%). But you still keep the money you earn from streaming services and music stores like iTunes, Spotify etc. You always keep 100% of that, minus banking fees/applicable taxes.