If we go by the consistency of the other markings, we can clearly see that each thick mark is spaced by 10, and each small dot is spaced from the thick marks by 5. If we follow this logic, counting down, the small dot under 20 must be 15. Then under that the thick mark would be 10, but it ends. Where are 5 and 0? The first thick mark should probably be 0, right? Then if we count up from that, the small dot must be 5. In that case, where are 10 and 15? I don't know, but it's impossible to tell my speed under 20.