Perhaps it's 123,456.7 Hard to tell without commas on the speedo.
It is a pretty absolute standard that if the last digit is a different color, then it is tenths of a mile (or kilometer). Pretty much all modern vehicles (which obviously doesn't include the C10) now have a hundred-thousand-mile (or kilometer) digit... which is a testament to just how much more reliable vehicles are compared to the past.
The second photo was when I had 123,456.7 miles on it... When I sold it I had about 138 k miles truthfully, I did snap a shot where it showed 34,567.8 but can't find it... I also shot one at 666 which I always liked.... heheheh