How does RR sort Reviews when you select 'Top'?

For a given fiction, you can sort the review by Top, Newest, Oldest, or Most Upvotes.  In the case of selecting the former, how does the website determine the order?  I'd assumed it would be upvotes minus downvotes = score, but that's not necessarily the case:
Why is 2up/0down above 4up/1down?  Obviously, the formula is different, but I don't know what it is.  Any ideas?

Edit:  Go to post #4 for what I believe is the correct answer!

Re: How does RR sort Reviews when you select 'Top'?

Talking on Discord I finally found out the formula Kanadaj set a few years ago (assuming it's still applicable):

Positive_Reviews means upvotes and Negative_Reviews means downvotes.  In this formula, more upvotes moves the review up the list, whereas more downvotes moves the review down the list, as expected.  The question is, which are worth more?  Upvotes or downvotes?  It depends.  If the review has a lot of upvotes and very few downvotes, getting a single downvote will have a big negative impact on the score, offsetting several upvotes.  If the review has about the same amount of upvotes and downvotes, I believe that means upvotes and downvotes are mostly cancelling each other out equally.  Here is a graph I made so you can get the gist of it:

I don't know what rating a review gets if it has 0 upvotes and 0 downvotes.