Dynamometer Results & Comparisons - Dyno Difference Question

I was talking to my tuner and he said that a guy got his car tuned at another tuner and the car did somewhere in the 525rwhp range. They had the sheets. Then the car was driven straight to my tuner, 3 days later, different state, same tune and made 485 on my tuners dyno. I dont know if dynoes are that different anywhere else, cause if they are, I really dont see the point. Oh and those numbers are SAE corrected. Anybody else come accross this?? I posted this in my MS4 dyno post but was actually very curious.

Different dynos and dyno operators can give different results, especially if you are going to two different brands of dynos. Like the auto manufacturers were prior to 1971 or 1972, there are no agreed to standards today in the chassis dyno profession as far as proceedures or methods of calculating HP/TQ. The main "point" of our chassis dyno is that it aids in tuning and before and after testing.

Yeah, that makes sense. They were both dynojets. Thanks again