The rep today on the dropdown is the total change today, not reputation earned today.

Example:
When someone removes an upvote on an edited answer for example, you'll lose 10 rep. This changes your delta for today (the popup), but not the total earned today (what's shown in the profile).

Another example, which seems to be the case here:
When a user is deleted their votes are as well, also affecting your delta but not the total for the day, so in these cases the numbers will be off a little.

You can recalc your rep at any time to sync these up at the bottom of your reputation history, available at: http://webmasters.stackexchange.com/reputation

The rep today on the dropdown is the total change today, not reputation earned today.

Example:
When someone removes an upvote on an edited answer for example, you'll lose 10 rep. This changes your delta for today (the popup), but not the total earned today (what's shown in the profile).

Another example, which seems to be the case here:
When a user is deleted their votes are as well, also affecting your delta but not the total for the day, so in these cases the numbers will be off a little.

You can recalc your rep at any time to sync these up at the bottom of your reputation history, available at: https://webmasters.stackexchange.com/reputation