Hmmm, the HP to the wheels seems to be off for your dyno run? EAS had a stock F12 M6 put down around 503 rwhp with a bone stock F12 and you're saying that WITH the GTC exhaust, it added 14 HP and only put down 501 rwhp?
The other thing I noticed about EAS' dyno run, compared to the M5's they ran on different days, was the outside temp. I believe it was 20-25 degrees hotter the day they ran the F12 M6 (109 degrees?) compared to the M5's (70-88 degrees?).
A couple of M5's, which ran on cooler days, put down 25-35 more HP to the wheels.... Something seems off here since yours has a GTC exhaust and there is a gain of 14 hp?
Nonetheless F12M6MD, you have a beautiful car and the exhaust sounds amazing too!