I've only got that number once. It was late at night and I was doing some pattern work for currency. Apparently the tower was trying to drop "suddle hints" when they were talking to me, but I completely missed it (although I did think their choice of words was odd). So I land, get the number and call them. They tell me when the tower says taxi back to the runway with me, I need to answer "wilco" and not to repeat what they were saying, and other things like if the tower calls you by part of your call sign, even if it's just Cessna tango, then reply that, and no more. Anyway, as it turns out, they had a lot of residents complain of unnecessary noise recently and tapes were getting pulled, so the tower was trying to help out the pilots.