Wellington, (the dog) & unnamed skunk sneezed 13 times, combined. Wellington sneezed 11 times & the unnamed skunk sneezed twice. 11 + 2 = 13.
After Wellington, (the same dog in Doggone Cats (1947)) notices the skunk's vacant house, it goes in quickly, to the warm bed. There is a sign on the door of BACK in 1 HOUR (in blue letters), referring to the skunk's soon arrival. When Wellington shut the door, the sign stayed on the door but flipped around, with DO NOT DISTURB! (in red letters) on opposite side of the board.