Size (Sz) does matter! Based on the virtue of their bulk, bigger characters will be more resistance to injury. Size for a character or being is determined by race or species and measured on a scale from zero to nine. Bigger characters also inflict more damage with natural weaponry.
“While green Martians are immense, their bones are very large and they are muscled only in proportion to the gravitation they must overcome. The result is they are less agile and less powerful, in proportion to their weight, than an Earth man, and I doubt that were one of them suddenly too be transported to Earth, he could lift his own weight from the ground.” (PM, III)
MASS is a measure of the weight as well as the bulk of an object. An object might actually be relatively light (low weight) but because of its low density and shape might actually have a relatively large mass rating. Since no Barsoomian measure of mass is described in the chronicles, in this game simulation, mass is measured in mass units (abbreviated #) being equivalent to a little more than 1 earthly pound (about o.5 kg).
Image from Frank Cho