TFS lease: is it per machine or per instance?

It seems that a TFS server is happy to dish out leases to any number of requests as long as they come from different application instances running on the *same* machine.

Is this a correct observation or I am doing something wrong?

Thats only partially correct.

Currently in TFS 4.0 and lower it grants a lease per user session on a machine (not just on a machine level - user session is accounted for)

In 4.1 were adding the ability for you to limit leases for indivdual instances of your app.

Thank you. Looking forward to 4.1