The Neighbors Top 10 displays how well your avatar did in the Fash Cup in relation to your neighbors.
If you appear in the list as the 10th among your neighbors, it is a good idea to refresh your page. If you have not refreshed since the results were announced, the game will automatically place you in the number 10 spot, even when you did not score high enough to place there.
There are no rewards for appearing in the Neighbors Top 10, but your Tiara Points are displayed to show how well you did overall. Diamonds will only appear as a reward if you also placed in the Global Top 10.