I believe that the bill says that money must be used above and beyond what is currently being used.  So that money must be used for 'extra' people and things.  So if 30,000 people are retiring, they would need to hire 30,000 PLUS whatever that bill is giving them.

I'm not sure where Time came up with thought that the IRS would only hire 30,000 new employees, but it was one of the Congressional people or committees that originally came up with the 87,000-ish amount.