Inadvertent Facemask Penalty

Question
In a Pennsylvania HS varsity game, offense first and ten from their own 30.  QB passed for 4 yard gain, and a flag for inadventent facemask.  Ball was marked on the 39 yard line, first and 1 to go.  Should that have been second down and one?  If inadvertent facemask should happen to be automatic first down (is it?) why was it not first and ten from the 39?  The defense's coach did confer shortly with official, and did not protest, so I'm assuming this was a correct call, but it seems confusing to me.  Thank you.

Answer
Dave
Thanks for your question I have just returned home form working my college game and as my profile indicates questions asked over the weekend during the football season will have a slight delay as I am not available to answer questions while I am working and traveling to and from games.

First-the incidental facemask penalty 9-4-3(h)is not an automatic first down. It is just a 5 yard foul.  This occurred on a pass play and I presume it was a live ball foul and not a dead ball as that would likely be a personal foul Major Facemask.  In your play the foul occurs after the competition of the pass and at the end of the related run (the run after the catch).  Therefore the Basic Spot per 10-3-2; 10-4-4 is end of the run (the 34 yard line.).  If the penalty is declined it would be the result of the play 2nd and 6 from the 34 yardline.  But if accepted it is 1st (down replayed) with the foul administered from the end of the related run - thus resulting in 1st and 1 from the 39 yardline.  There are some difference in the penalty enforcement rules between high school and college and the NFL.