Recent achievement count from the indicator and dropdown are not matching. One shows +13 while other shows +15 (3 upvotes)
The reputations tab does not show any negative reputation points
Here is what likely happened.
You did get +15 yesterday and for a while, the top bar did show +15 in the green box. Then, something that gave you +2 reputation in the past has been removed.
The achievements dialog does not show such things, however the -2 does affect the overall count.
You might be able to find the culprit by ticking "show removed posts" checkbox in the reputation tab of your profile page, but this might not help if for example you suggested an edit to a post that has been deleted.
This reputation change is affected by changes from all Stack Exchange sites you are already registered with, so you will have to check reputation tab on profiles on all those sites too.
-2
points. Make sure "show removed posts" is checked at bottom of your rep page.