UE4 Profiling performance

UE4 profiler

This is inside UE4’s profiler.
In a previous question you answered that those two stats (CPU Studio and CPU Mixer) are in CPU percentage.
Here they appear as ms on the graph.

Is it an error?
Does these two stats have an influence on the GameThread (ie the GameThread can only use the CPU % left)?
On a low-end machine, I get 20% on the CPU Studio, can that be a performance bottleneck?
How can I “convert” CPU percentage in ms for easier optimization?

Thanks!

The CPU (Studio and Mixer) values are percentages of their respective threads, which are both separate from the GameThread. The profiler shows all numerical type stats as a value, and the only axis on the profiler are ms or KB.