Explain link syntax

The README.txt file provides some examples of subscribe and unsubscribe links, but no breakdown of what the components of those links represent. A person new to this module is not necessarily going to know what is meant. For example:

http://example.com/subscriptions/add/type/forum/12

It took a fair amount of debugging for me to tentatively conclude that this is

http://example.com/subscriptions/add/type/content_type/uid

and means "subscribe to all nodes of type content_type owned by user uid"

Maybe this belongs in each submodule instead, I can see the logic in that. But some kind of help or text somewhere would be useful.