Honda CMX500A 2019 Owner's Manual page 30

Instruments
To reset the tripmeter B and average fuel
mileage B together, press and hold the SET
button while the tripmeter B or average fuel
mileage B is displayed.
Tripmeter B
26
(Continued)
Average fuel
mileage B
or
When they are reset, reset display appears at
each indication. Then, the display returns to
the last selected indication.