You have to understand that bow companies publish the IBO speed of their bows, which in most cases cannot be obtained in a hunting type set up. IBO speed is calulated using a 350 grain arrow, 70lbs DW, and a 30" DL. While the 70lb DW is not a problem, the 350 grain arrow and 30" DL is a problem. I stand 6'2 and have a 29.5 DL, so you have to be a pretty big bow to get a 30" DL and DL is a super important factor concerning the speed of you bow. This is not to mention that you would have to be shooting a super light arrow setup to get it down to 350 grains, not to mention a 350 grain arrow out of a 30" DL.

With all that being said,your number does seem a little low for your set up. I would have guessed you to be in the mid 250's to low 260's. Maybe run it thru another chrono and see if you get a different reading. Or, as you said, you are happy with the way you are shooting, leave in alone and don't worry about it.