Relation beetween Resolution quality, screen percentage and resolution scale

Hello everyone,
I am developing the video settings for my videogame and my feeling is that there is a lot of misunderstanding about the 3 concepts of:

  1. Resolution Quality
  2. screen percentage
  3. resolution scale

What is the differences and the relation between them ?
Furthermore: are they related to the screen resolution (eg: 1080p, 4k etc…).
Should the resolution scale tuned-up related to the screen resolution or are they standard values ?

For example I have noticed that unreal is using standard values for resolution scale:
Low Scalability → 50
Medium Scalability → 71
High Scalability → 87
Epic Scalabilityh → 100

How are these values ​​calculated?

Please also note that In the Editor this value is called “Screen Percentage”, but the blueprint node to change that value is called “SetResolutionScaleValue”, so my perception is that screen percentage = resolution scale.

Thanks in advance