EasyGoing1:
For example, this image for the pinouts shows that pin numbers D11, D12 and RESET are actually pin numbers 15, 16 and 29.
15, 16, 29 are the physical pins on the ATmega328P microcontroller.
EasyGoing1:
But this document shows those same pins as 14, 15, and 3.
That's the pin number on the PCB, counting counterclockwise from the top left corner.
They're both correct, just referring to different things.
EasyGoing1:
How the heck do I know for sure which numbers are literally assigned to each pin on the Nano?
The Arduino pin numbers are written right there on the silkscreen of the board. Use those numbers in your Arduino code.