Hahahah, same! I use a folders named as the hostname to build that machine's config on the fly. And all my config files are in one repo that then I stow
making the BOLD ASSUMPTION that the angle of the arch is 90deg (the bottom right corner of your diagram), then the dashed lines will lead you to the value of the bold line.
If the original assumption is correct, then the answer is 15.
TKL for the win