The length of the red arrow is always the same. When your velocity is zero, your "time speed" is 1.0. As you begin to move faster, the arrow tilts towards the X axis, decreasing your "time speed".
The biggest issue is that the interchange between speed and time is not linear. So that graph doesn't make sense as displayed.
At a minimum you have to understand that the time scale on the side of the graph is not linear, but rather exponential. And graphs with exponential scales are not easy to understand.
Making it worse is that there are other things that can slow down time - namely acceleration.
I was mostly responding to TomGullen's confusion about the GP's statement, rather than trying to paint a super-accurate picture.