"Top Answers" are answers that are supposed to best represent you as a candidate, not necessarily those which have been most up voted (although it stands to reason that they may be one in the same, in many cases). As far as I know, the system isn't meant to automatically update them, even if it did some prefilling originally.
Thankfully though, you have full control over what's displayed there:
If you want to remove the existing answers, use the red × in the top right corner to take them out of the list. If you want to add new answers you feel are better candidates, use the "add an answer" link at the bottom. If you choose to display multiple answers, you can sort them to your liking using the arrow(s) next to the remove button.