Extruder steps - not sure

K8200 3D Printer K8200 - Printer software (repetier, slicer, ...) a
1

I have done extruder swap to 1.75mm filament feeder and some (I think) fake E3D noozle - 0.3mm.
I’m not sure about setting the steps per mm:
Should it be mm of filament comming in or out?
I set it by what is comming in and I get big overflow… I think (I use ABS and flex mostly) the material change volume with temperature… But how it will calculate the needed filament then?
Another solution could be setting the noozle diameter by actual diameter of fillament comming out of extruder (maybe?).

EDIT:
The filament comming out have 0.4mm diameter maybe the seller of the noozle have bad information…

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You specify the steps/length of filament going IN. You can calibrate your extruder steps by marking off some length of filament from the extruder inlet, for example 10cm, then extruding that length and seeing if the mark reaches the inlet.