The reason why I ask is because I really thought that mine used to air test deeper than 5" on a quarter. I took it to the beach at the end of last year to detect in the salt water. It hasn't been the same ever since. So I thought I'd compare with yours since it is new.
Anyway, I've definitely found things that were over 6" deep before. It is a very easy machine to use and does a very nice job for the money. Enjoy your new machine!