Vandersteen tilt question

When looking at the manual’s tilt chart “distance from speakers”, is it looking for:

1. Distance from listener to plane of speakers, or

2. Distance from listener to each speaker.

For example (for illustrative purposes only, not suggesting this layout), if speakers and listener formed a triangle, with distance between speakers of 12 feet, and the other 2 sides 10 feet, would the chart be looking for 8 feet, or 10 feet?

I’ve had numerous Vandersteen’s and always assumed it was looking for number 1 above. Anyone know for certain?