Icon size for buttons dont working

Hi, thanks for the plugin updates, there are more and more plugins for the classic editor abandoned, it is appreciated that some plugins are still working.

I can’t get the button icon size to work, it’s also not clear what is the parameter to use, you don’t specify it in the plugin referencer:

should it be 4, 4x, 4px?

Also no option works for me.

Thanks for your help.