I think it's around 20% fees in total, but part of the fees are used to fund delegators. It's explained in this post:

https://steemit.com/vimmtv/@chiren/why-i-m-delegating-to-vimm-support-a-steem-project-and-make-some-gains-on-the-side

When a streamer gets upvoted on Vimm.TV, 81% of the rewards go directly in the streamer's pocket. Then 9% goes to @vimm.pool and is distributed to delegators based on the size of their delegations. The remaining 9% goes towards @vimm to help cover server costs, community events like #vimmraidday, giveaways, and future tournaments.