I've been reading a decision from 93' - throughout the decision the court refers to the one claim as "count". is there a difference or are these interchangeable?
Claim = what you see in a patent. There's a listing of claims at the end of a patent document.
Count = each cause of action in a lawsuit.
If you infringe a patent claim, then that's "one count" of patent infringement (one cause of action). You can infringe one, some, or all claims in a patent. So you can have one count or any number up to and including the number of claims.
You can also have other causes of action (like you also broke a contract with the other party) that could increase the count, but this is the basic answer.