That's the ENTIRE point of the setting.
It's the adjustment factor that makes it so when you measure filament and enter the value, it then works as expected.
Important: that value is different for different types of filament. Your 5th gen is generally designed to use PLA. However, if you try other plastics- because the material is different and the teeth of the drive gear grip it differently- then that value changes.
So for ABS it's one value, for PLA it's another, and Flexible filament might be a third value.