Hi,
I don't know how difficult my explanations are to understand, but when I write "for a capacity check by number of HUs you use the "capacity check by key figure packaging material"", that should mean - there is NO direct assignment of how many bins you can putaway in a bin (at least there is nothing I know).
This field you show is not for that. The F1 help unfortunately is not really helpful, but the tab "Bin sectioning" should tell you already that this is for something else (Putaway and Stock Removal Strategies - SAP Library). This is not what you asked for, because this is for a dynamic segmentation of a bin (and each segment is then like its own bin).
Brgds
Juergen