Speedometer Gear Charts - Clarification/Differences

Just a note...

Someone recently noted that their speedo was spot on for speed but off for miles.

Meaning, clocking mile markers, 5 miles was 4.9

But gps and speedometer read 60 mph.

Turns out there is an adjustment inside the speedo head. First get the gear the correct size for miles, then adjust the adjuster for the correct speed.

A bit hard to do and you can not do it on the car.