The 8.1 hours that Lartsa quotes is not unreasonable. However, it is always interesting to check in the logbooks to see when the pre-delivery hours were flown. Hours flown after the issue of a C of A would be more suspicious unless this was to test the installation of optional equipment.
If it niggles ask your supplier for a break down of the hours? If your helicopter had been used to demonstrate the aircraft to another possible buyer they may well be able / willing to compensate you for the any component time consumed that you consider unreasonable.