The Hierachy/Schematic editor uses I think only the first 3 attributes. The rest of the attributes are reserved for the netlister tools and backannotation. Some tools could be setup for the right attribute number. The attribute numbers between 240 and 255 are for special pupose as symbole color highlight. But doc is bad regarding this.
I read that some of the attributes numbers could be used by the user, but I don't know which they are. Because you don't want to use something which is reserved by C0hesion for future use.