How much is extra credit worth?
ONE POINT PER MONTH, MAXIMUM.  Each month's extra credit is worth 1 full point added on to the FINAL grade at the end of the semester, after everything else is scored and averaged.  That means if you have an 87%, B, for your final semester grade, the extra credit (if you do all five month's worth) brings it up to 92%, A.  Although 1 point doesn't sound like much, it's a lot if it's added to the final grade as in this case.