How is "most of" handled by Inform 7?

I am trying to port an Inform 7 story to another authoring system. I use the natural English like source tekst which I find to be pretty clear, although I’m not a native Inform speaker. When I don’t fully understand the source I play the game to that point and see how it behaves.

Now, the source has the following code:

if most of the rooms are visited begin; <do something>; end if.

I’m trying to understand how ‘most of’ should be interpreted. Is it all but 1? all but 2? 80 percent? Playing the game doen’t really help to find out.

I hope someone can explain this or point me to the right section of the manual.

Thanks for reading.

§6.15. All, each and every

Thanks, Vince.