I recommend you don't try it without the proper equipment to perform the full calibration which is a P-S test box and encoder test box.
In the USA an owner making that adjustment would be contrary to the CFR's, I imagine it's the same in CA.
I had one of these and found out the FAA pulled their TSO and PMA due to non-conformance with the specs. Mine was reporting my altitude more than 300' high. I replaced it with an ACK 30.5 encoder-along with getting my GTX-327 software upgraded. No complaints from ATC now.