Twelve names sign. The hour runs out. The twelfth name pays 0.003 across the other eleven: each takes back 0.003 + 0.000272 = 0.003272. The twelfth takes back nothing.
Had a thirteenth name signed at minute 59, the twelfth would have been paid instead: 0.003 + 0.00025, and the thirteenth would pay the room.