When trying to compare numbers generated on different dyno's, you need to know what gear the run was made in (for instance, some dyno operators will use 5th gear rather than the normal 4th, and this will have a significant impact on the numbers). You also need to know what correction factor was used, if any. Correction factors are used to "standardize" dyno results for various atmospheric conditions (temperature, humidity, and absolute barometric pressure). In the USA it is normal to see SAE corrected numbers, while in Europe the DIN system is normally used. The chart should specify the standard used on the test, as well as the actual atmospheric conditions at the time of the test. Other factors such as the physical condition of the dyno itself can affect the numbers - ask when the dyno was last serviced and calibrated.
Outside of a major laboratory, dyno results shouldn't be taken too literally. There are too many variables that are not controlled or even measured in a typical DynoJet installation, and too many ways for either an unscrupulous, or just plain ignorant, operator to affect the results. Rather than try to compare your final results with someone else's from a different dyno, get a good baseline run prior to your modifications and then compare that to your final numbers on the same dyno with the same operator. As an example, say Joe gets 85/100 stock, and 95/110 after stage 1 mods. Ralph goes to a different shop, and his numbers come in at 90/105 stock, and 100/115 after stage 1 mods. Rather than look only at the final numbers and assume that Ralph got the better tune, look at the before/after differences and realize that both people got a 10/10 increase from stock.
Jerry