Yep, that can be a easy fix.
Remove tacho from cluster and there is a small white sticker on the back of the housing.
Behind this sticker is a small screw which is a pot (variable resister), and you can adjust as you need.
I have used my multimeter tacho before and adjust the tacho to read the same.
Just be careful if you run the car with dash remove to re-connect oil pressure gauge or your front floor will be covered in oil.