It doesn't seem a bug to me. I think this is the order of events that caused this:
- You gained +10 reputation on an answer;
- You have hit the achievements indicator. Counter reset;
- You got two suggested edits approved;
- You gained another +10 on your first answer.
The count you see is of the last three (from the moment you hit the achievements indicator). 2 + 2 + 10 = 14.
Since the two upvotes occurred on the same day, their total score is shown, not the gain from the remaining upvote (the one you didn't see yet).
This means the +20 is highlighted, while you didn't see just 10 of those points.