If you are having issues with your speedometer there are usually 2 reasons...
1) Your Speedometer Reads 50MPH While Riding
If this is the case, then the most likely culprit is the Speedometer Ratio has been accidentally changed within the LCD computer. If you enter the settings menu make sure to change screen 5 to the number '6'. This should resolve your issue!
2) Your Speedometer Reads Slightly Higher Than it Should
If your speedometer reads slightly more than a GPS computer or other bike, this may be caused by the tire pressure of your bike. The speedometer has been calibrated for a fully inflated tire. If you are riding with reduced tire pressure this will reduce the effective tire diameter while you are riding and actual land speed of the bike. The difference is usually minimal and should not affect your ability to enjoy your awesome electric bike.