The first descriptor corresponds to the top-left edge of the roof of no. 17 (x=223). It is used to check whether Sam is going to step off the roof or away from the edge of the roof (see 41238).
50048
DEFB 130,195,2
y=6, z=1; left, right
The next three descriptors correspond to the far left walls of no. 17 (x=223) and no. 15 (x=239).
50051
DEFB 18,64
y=13, z=1; right (top floor)
50053
DEFB 30,64
y=19, z=1; right (third floor)
50055
DEFB 42,64
y=25, z=1; right (second floor)
The next three descriptors correspond to the doorways of the shops under no. 17 (x=223) and no. 15 (x=239).
50057
DEFB 221,76,65
y=33, z=1 or 2; right, down/left, down/right (door open)
50060
DEFB 58,64
y=33, z=1; right (inside, door closed)
50062
DEFB 122,76
y=33, z=2; right, down/left, down/right (outside, door closed)