Yeah it can happen that way. If you know the date and location of the dyno test you can look up the local weather and figure out what the correction factor should've been. Then compare that to what the dyno shop used. Also check the inlet air temp if that is on the dyno sheet. Sometimes the shop will have the inlet air temp sensor located to close to the engine so the temp will be higher which then provides a bigger correction factor. The inlet air temp should be close to the outside air temp or a few degrees warmer. Dyno numbers are fairly easy to verify if you know what to look for.