Just watched it for the 2nd time, and I really enjoyed the film as I do most David Mammet scripts.

I'm having difficulty understanding it, though.

Shelly "the machine" Levene admits to office manager Kevin Spacey at the end of the film that he was the one who robbed the office. He even has the money to prove it.

But at the very end, the Alan Arkin Character, who we thought robbed the joint, picks up the phone as soon as there's no one around and dials a hot lead: presumeably it was one of the stolen ones that Levene sold to the rival office.

How could they have BOTH robbed the joint?