Adding Fermentables Later in Ferment

I am brewing a beer that calls for a maple syrup addition a couple days into fermentation. I have read that adding fermentables later in fermentation is done so that the yeast will have a chance to use up the extract/grain sugars first. In estimating the final alcohol content, do I need to add the extra addition (maple syrup) to the OG? Also, does adding the maple syrup later in the ferment have any effect on the FG (i.e., will this take the FG lower then it would have been had I not added it later in the fermentation)? Your help is greatly appreciated.

yes for your ABV calcs you need to add the maple syrup to the original gravity. I call it Calculated original gravity.

Adding the maple syrup later as opposed to right when you pitch probably will help you attenuate better, that's kind of the point. By adding the maple syrup later you are #1 giving the yeast a better (lower gravity) environment to ferment in and they'll stay healthier, #2 (as you mentioned) it makes them eat the tougher sugars first, then they get the easy maple syrup sugars.

Thanks for the response! Very helpful!