I think that might've been part of the numbering through the exhibit to align with the audio companion. They have to be making money hand over fist. It was like $40 to get in, $50 for entrance with a souvenir poster (which was just their spray can logo), $75 for a VIP experience which as best I could tell was a lanyard and an exclusive lounge room that was just a couch and a chair in a roped off area, another $20 or whatever for the audio bit, a program for like $25, and a gift shop full of bastardized Banksy art on cards, canvasses, t-shirts, magnets, you name it.
So the gangsta rat must be really small, like a sticker or something, or the number is really big... Strange either way. But thanks for the information nevertheless! It is a shame that nearly every unauthorized banksy exhibition is a shameless cash grab.