I don't have that one but I do have in front of me a "Speedohealer" model SH-V4 that I have been meaning to install for a couple of months now. Just haven't had time to get to do it yet.
My factory speedo reads sixty but my GPS reads Fifty four mph. Same percentage on the odometers. By not fixing this issue, the factory gets off the hook faster on warranties if they have mileage stipulations and you may ride a little safer than you think.
Yes, a correction is in order and this is a very old issue.