Primimg Sugar In The Boil

Made a Black IPA that called for 1lb of priming sugar in the boil. Recipe said to add it at flameout. I added it at the beginning of the 60 minute boil. I didn't achieve the OG that I expected. Recipe states OG is 1.076. I ended up with 1.067. Is it possible that I got the lower OG because of when I added the sugar? My efficiency typically runs in the high 70's. It was a 60 minute mash at 152.

Thanks

Your OG has nothing to do with when you added the sugar.

Priming sugar is " all the fermentable sugars that have not yet fermented when you bottle or keg". They can be present already, or you may add them just prior to kegging / bottling. This pound of sugar is not priming sugar, it is an addition to get the final ABV higher.