It means that some features won't work, like the stylesheet editor, which needs the correct permissions for the styles to actually be changed from the control panel.
I set all folders to 777 and all files within each folder/directory to 666.
https://www.ubbcentral.com/doc_install.php for the full set of instructions which includes the deal for Windows servers too. I see that the documentation has missed the fact that there are images inside the admin directory.
