For project extra credit, the points you got are normalized by the total for the regular project and multiplied by the weight
(so if you get 10 extra credit points on a project that is graded for 50 pts, and counts for 10% of your grade, then you get (10/50)*10 = 2 cumulative points)
The UGs got extra credit for doing the midterm at home (it was counted as 3.5 cumulative points)
The UGs also got extra credit if they did the last question on the final ( which counts for [x/100]*15 cumulative points)
The social networks extra credit homework counted for 3.5 cumulative points.
All said there were a maximum of 14 cumulative points that one could have amassed.
This will likely be the last mail about the class cumulatives. You should be able to find your letter grades from the registrar as and when they get posted.
Wishing you all a wonderful (if all too brief) holiday season.