http://ageod.nsen.ch/aacwwiki/Manual:Combat_in_the_field
One hit is a strength-point hit. As you notice from the manual, units usually don't stand in the fight and die, but rout away before being eliminated (you can see how many of your elements routed from the lines at the battlereport). Thus the damage is usually spread out over several elements, and you don't indeed see that many eliminated elements.
"Global combat value", if I understand correctly, is the power of all the units taking part in the combat added together +/- any effects affecting (for example +10% if they have a supplywagon present, or the possible malus for being non-active, etc).
There are three kinds of people: Those who can can count and those who can't.