I don't think it is a bug. It is how it works. Color changes take only place at multiples of 5, so max. is +55 or +110 from minimum speed. Take first picture minumum speed is 10 (rounded down) so so max. is 65 or 120. It looks from color that some speeds are a bit higher then 65 maybe 70, so it takes 120 as maximum also no speed reaches this.
I have now reduced multiplyer to 2 for next update.That gives much closer ranges so it is easier to see where limits are.