Compression Test

Hi, I had a pre-purchase check done on a Mazda RX8 Series 2 earlier today, completed at a performance workshop which specialises in street mods, racing, etc, and the website states that they specialise in rotaries. The compression test came back with 80-95 PSI. The mechanic said that this was fine, and that his gauge always comes back with a lower reading, and that he can test a turbo and return a 75 PSI reading so the RX8 will be fine. I'm aware that the ideal PSI for a RX8 is 110~120. I believe he used a piston compression gauge, judging from these numbers, but I'm not sure. Is this a reliable reading? I'm not sure if the guy selling me the car will be willing to drive it to another rotary specialist as the next one is a fair way away.