Odometer adds mile at 9/10. Is this common?

My odometer on my 1985 245 shows 230,000 miles and some change.
Everything on the cluster works, except the odometer adds a mile with
the gauge hits 9/10. Not during 9/10, but a solid new mile when 9 out
of 10 hits. I did a calculation that 9 out of 10 = 0.9 and 0.9 X
230,000 = 207,000.

So, if this odometer has done this since day 1, then it's about 27,000
miles over. If it's done it since 100,000 miles, it's about half of
that over.

Any ideas?

Jamie

 

I got a reply that said if the odometer is turning a new mile ON the 9
every time, that is still a full 10 digit range (0-9 is 10 digits).
Therefore it is still a full mile. They said a 9/10 mile would turn a
new mile on 9, then 8, then 7...

thanks.