Nothing is ever clear with Apple when it comes to commercial use.
I tried to understand that part in the SLA and found it quite difficult. What I think I boiled it down to was you needed 1 license per user/Computer combination. If you have four computers, but only one user on those four computers, then 1 license. If you have different users on each machine, then I would think you need 4 licenses. And, since it says "employees," I don't think the users include you, the owner. If your four users ever only use two Macs at any given time, then it sounds like you'd just need two.
When I use the term "user" I mean actual people, not the accounts on the computer.
But, that's just my understanding. I'm sure someone else could come up with another.
It's unfortunate that it requires a legal department to interpret that SLA.
That article AnaMusic linked is just the "how to do it" not whether it is legal or not.