The last time we cruised, I checked out the table we had on the prior cruise and it had a different number than when we had it. My guess is that depending upon the number of guests and the make up of the groups that the table layout and numbers can change slightly from sailing to sailing. It's just a guess and I'm going to look into it more on our next cruise.
Maybe Barb and Tony know if the table numbers change from sailing to sailing (since they've been on so many and did the 3-peat!)