I think TSA calls the number you want your "Pass ID" or something like that. If you log on to the Global Entry website it is clearly listed on the opening page I think.

At my home airport unfortunately the word got out on Trusted Traveller so the line has gotten longer. It still moves very quickly so it's not much of an issue. I commute a lot up for short call and I pretty much detest commuting in uniform so I use it a lot.