The speedo error is non-linear. With stock gearing it is about 7-8% optimistic at freeway speeds, but riding around at an indicated 35mph on surface streets it is almost dead on accurate. As your speed grows so does the amount of error so by the time you are at an indicated 130mph the % of error can easily be 13-14%
If you have lowered the gearing with a 15/41 kit expect that 7-8% error at freeway speeds to jump to about 12-13% depending on your rear tire size.
What is really interesting though is even with the optimistic error built into the speedo for stock gearing the odometer is still accurate so they did it on purpose when they engineered the bike.