Quick question regarding PrusaSlicer  

RE: Quick question regarding PrusaSlicer

PS doesn't in general work like that.  If you set 0 (Auto) then speeds are 'limited' by other things,  the main one being the max volumetric flow setting, be aware there are 2 places than can be configured, or some of the other settings like Max Print Speed.  You  must be in Expert mode to see and set most of the speed settings btw.

If you don't set zero or a fixed speed but use a percentage based one then the tool tips for each speed setting will tell you which other value the percentage is based on.  Tooltips are your friend (mostly) but ignore the' suggested' Default values in them.  They are legacy things.

I will also point out that the whole thing is a bit of a mess with it easy to get confused unless you have been using the software for some time and are used to its quirks.  Setting non fixed speeds can sometimes give you strange edge cases and do unexpected things (as the issues on github will attest to).  Probably as its one of those areas that has evolved over time and become convoluted.  It probably needs a complete refactoring in code, but that's Prusa's call lol.

One other area that often catches people out is that there are several Filament based settings around cooling that can ALSO effect print speeds.  For example one of the places you can define Max Volumetric Flow is also in the filament settings (it will use the lowest value).  The Slow down if layer is less than xx is a real common one that gets people who wonder why things are printing slower than they expect.