Between 3 and 4 on the sundial, there are 4 sections marking the quarter hours and then these are subdivided into 3, marking out 5 minute intervals. Hence the sundial gives the time as 3:40 when the watch says 3:48. This is most likely just a slight misalignment when the sundial was fixed. One hour is worth 15 degrees so 8 minutes represents a 2 degree misalignment.
