OK, what DoctorWho said jogged my memory. If 3/4 cup is used to backsweeten a cider that has reached FG, and this will create a normal level of carbonation, then ~ 3 point drop is what this correlates to.I think it should be the same (or be so slight as to not really matter) as what ever the reading was before you bottle. The sugar you use to prime will raise the sg a slight amount but then as the yeast eat and turn out alcohol and CO2, the sg will drop back down a slight amount.
But I have never done an actual reading to confirm.
Ok, now I see what you are saying...You are raising the sg with sugar, bottle conditioning and then pasteurizing. That would deviate from the normal priming methods. Sorry, I am not sure as I have not done it this way yet.
Yes, I understand. However, I'm trying to not end up with a bone-dry sparkling cider. I back sweeten enough to create bottle-bombs if I don't pasteurize. I (and much more importantly, swmbo) prefer semi-sweet sparkling cider, and this is a little more complicated.DoctorWho is right. The yeast ate all the sugar until you reached your final gravity. By adding priming sugar you are raising your gravity. They yeast will eat that sugar until it's gone and you will have the same gravity as before.