Originally Posted by Starwood Lurker

Could be one of two scenarios, I'm thinking...

There are a couple of "business" levels in SPG: Corporate Preferred and Starwood Preferred Business.

But, since he mentions three levels, he is most likely making the distinction between his SET account number being SET, SET/SP or SET/GP. That is determined by his company's level of participation in the SET program determined by the number of room nights they commit to.