my slant buildup

got a call from machine shop yesterday, says chambers on head are at 60cc, Im surprised they came out that large. so now I could tell him how much to shave, I want to get down to ~46-48cc.... I told him from out of the air calc (hey I was driving at the time) to shave 70 thou.... I later figured out the 0.0066 per CC wanted removed, looks like maybe I should have told him closer to 80?
He did say it "checked out at" 60, which was the same as what he looked up and was listed as "typical/common".... I do know taht machine shops do have more access to such info than we do, I wish I had some of their resources.... He did say that it came out as 60cc, same as what he was able to look up, makes me wonder if he actually measured mine.... he is putting my O/S SI valves, into it.... which even if that was all that was done, that would alter the chamber volume, wouldnt it? HE also finished my porting job and is supposed to be putting seats in on the exhaust side per my request. Nothing yet has been said as to whether he had to do any guide work, I was anticipating it for sure.