Translated:
Good morning, I recently purchased a Durkopp Adler 69 and while studying how it works I came across the adjustment of the pressure of the feet; I know that the larger threaded part is used to adjust the pressure of the feet but, despite my attempts, I can't understand what the small screw at the top (circled in red) is for, so I'll ask you.
@GIULIO English is the language for this site. Please comply.