Trying to understand subuser settings

I set up the Subuser plugin, and created a situation where subusers get access to the same product as the parent.

Now when a subuser is created, they can create their own subusers, the same number as the parent. Clearly, this is not correct.

Am I supposed to create an identical product for subusers, with the exception of the ability to add subusers?

Or am I missing something simpler?

I see, I guess that makes sense.

So, is it reasonable to think I could have one product level, and just sell blocks of users that would be added to the main user's account? Then subusers that the main user adds would have the same account as the main user, but without the purchased subuser blocks?

Can a subscriber add an unlimited number of the same product to their subscription? (i.e. multiple blocks of 5 subusers)

Great, thanks Alexander.

One last question. On the product setup page, there is a checkbox setting that would allow the user to change the quantity. I check this box, but that does not seem to change anything on the order form. What exactly is that setting supposed to change?