I have read the opening post several times and end up concluding it is all about defining starting points and what is being measured. Semantics can easily trip one up if common definitions aren’t used.
Mile markers go from west to east and south to north. If the highway starts at the state line, mile 0 is on the western state line, and the total length from the western state line to the eastern state line would be the mile marker close to the state line. If a highway doesn’t start at the state line, mile 0 is either the westernmost or southernmost beginning point of that highway.
The key is the unit of measure between two points and not the number of points. People count the first step after the first step is taken, not while standing still before walking.
To be honest I never really thought about this. Generally in most of the buildings I have been in the first digit is the floor identifier with regards to office number. I have been in a few buildings where in the elevators the ground floor was “L(obby)” and they counted up from there (1,2, 3 etc).
This is why semantics play important part in giving directions. The instruction “mop floors 8 to 11” could be interpreted by some (or many) as mop floors 8, 9, 10 and stop at 11. Just as when you run a race, you run to the finish line. There is no point in running after that. It would have been clearer if the boss said “mop floors 8 thru 11”.