If its like .5 under on an oz, its pretty much what you asked for. That much could be accounted for by a difference in scale calibration or maybe it has dried a tad since being weighed out. It doesnt always mean there was a pinch. But if it was a pinch its a small one and mentioning it might be more of a hassle than ignoring it. Depends how well you know him and how often you buy.
If hes your only , or best, connection dont risk insulting him over a little nugg.
Smoke one and youll be more likely to say 'no worries'.
enjoy.