Back Spacing, which way?

Nice job of explaining it Blu, and a good illustration.

The only thing I would add for clarification to what Blu said is that when he is describing the offset (+6, +3, +16), that number is in millimeters. For some reason backspacing is typically called out in inches and offset is called out in millimeters. Don't know why, but wanted to clarify because it confused me for a minute too.
Because us Americans use backspacing, usually. The Europeans or Asians use offset. It's really the same thing, although offset is easier to understand, but backspacing is easier to measure.
To convert inches to mm multiply by 25.4, to convert mm to inches divide by 25.4.