Bounding box size, hmin and hmax

Hello Forum,
a couple of questions

  1. let consider a sentence like this, found in the on-line documentation:

“without metric, the minimal edge size is set to 0.01 of the bounding box size. The maximal edge size is set to two times the bounding box size.”

What exactly “bounding box size” means? Which size?

  1. Sentences like these, for hmin/hmax

[*] “without metric, the minimal edge size is set to 0.01 of the bounding box size”

or

[**] “with metric, the minimal edge size is set to 0.1 of the smallest prescribed size”

means that the parameters are always relative? If I would like to use the option [*], and give mmg absolute hmin/hmax values should I compute the “bounding box size” in advance?

Thank you
Giovanni