Hi, it's very difficult to explain in simple terms, but let me try nonetheless:

• you are correct that utopian posts are voted on in separate rounds than regular steem-ua posts;
• every post gets a UA_Vote score, which is then - per batch - ranked relatively to all other posts in the batch;
• each batch (= voting round group of posts) is allocated a certain amount of voting power (Mana);
• if more posts are to be voted per batch, there's of course less Mana available per post in the batch (for example lots of steem-ua posts to be voted on in 1 batch);
• and vice versa (for example only a few utopian posts in one batch)
• due to the "quarrel" between fulltimegeek and berniesanders - which is sad because both of them supports steem-ua, I like both of them personally, and they both more or less have the same stance against for example haejin - which caused ftg to use his delegation for flagging bernie, - as I interpreted his words on bernies post, and when a project - us - in this case, looses delegations (the 51,000 SP from ftg) you also drop in Mana (at that moment);
• so you are seeing a combination of factors that place things out of context