Sharing content when collaborating with others on a single apple numbers file.

I decided to share one specific numbers file with 2 other people. I Invited the first for collaboration with read only privileges. When I finished sending the same type of invitation to the second one, I got the following warning: "New participants will be able to see all items in the folder. Folder containing this item is already shared."

Searched for any info regarding this warning, but found nothing. Has anyone any idea if what is described in the warning is what actually happens when the user shares ONLY ONE FILE, or is this some bad- wording- issue and needs to be take care off? Do the people I shared ONE FILE with, have access to the whole folder containing the specific file?