Although it's not particularly clear when looking at this page (because the events didn't happen in this order), the complete summary of your reputation on this site can be summarized as follows:
More specifically, I think you're getting confused seeing the net +21 from upvotes and downvotes on the one question. Under normal circumstances it's unusual to see a post with such a large yet equal number of upvotes and downvotes, but I believe it's due to the fact the question was mentioned on meta elsewhere.
As others have pointed out, you need to have 1000 reputation on this site to see the vote breakdown directly, although there are some other solutions, such as a SEDE query or a userscript (see here for more info). However, unless you reach the daily 200 rep cap (or it's a meta question) it is usually easiest to calculate it via equations, where u is # of upvotes, d is number of downvotes, t is total net rep gain from votes (in this case +21), and s is net score (in this case 0):
- If question: 5u - 2d = t
- If answer: 10u - 2d = t
- u + d = s
(You have to make sure that you account for reputation from accepted answers, which is +2 if you're doing the accept or +15 if you get the accept. This isn't too hard of a calculation IMHO, since I do it all the time in my head for users who have only one post.)