Making mistakes is also a human problem, unfortunately. If you change the 8 to a 6, everything works, 300, 220, 350, 100, -50. My guess is a transcription error: the editors cleared the problem, but the typesetter fat fingered it when making a graphic.
OP mentioned that their Kid has not been taught the concept of negative numbers yet. So the -50 for the lower right part of the right “brick wall” wouldn’t make sense either.
Making mistakes is also a human problem, unfortunately. If you change the 8 to a 6, everything works, 300, 220, 350, 100, -50. My guess is a transcription error: the editors cleared the problem, but the typesetter fat fingered it when making a graphic.
OP mentioned that their Kid has not been taught the concept of negative numbers yet. So the -50 for the lower right part of the right “brick wall” wouldn’t make sense either.