Yes, basically every round it will upvote the highest scored contributions until the required voting power to upvote the highest scored remaining contribution will deplete the category's share (< 0%). For example (using made up numbers):
Category X has share of 1%
- Calculate usage of upvoting contribution A -> uses 0.3% -> category's remaining share = 0.7%
- Calculate usage of upvoting contribution B -> uses 0.29% -> category's remaining share = 0.41%
- Calculate usage of upvoting contribution C -> uses 0.25% -> category's remaining share = 0.16%
- Calculate usage of upvoting contribution D -> uses 0.17% -> category's remaining share < 0% so don't upvote contribution D and stop upvoting contributions in category X
So this means that category X will have 0.16% left in its share which won't be used, and in the next voting round it will start with contribution D (unless contributions with a higher score are reviewed in the meantime). I hope this contrived example clears things up for you, haha.
Haha it actually made a lot of sense (you wrote it in a developer's way so it helped a lot xD )
Thank you :)