Slitherine

I am new to the game, so sorry for silly questions:
I just don't understand the concept of impact combat. I read the manual text again and again but don't get it.

It says:
"In impact combat, only the men who actually make contact fight, so if a smaller unit charges a larger one, or vice versa, both sides initially fight with the strength of the smaller unit."

What does it mean "the men who make contact"? The first row of a unit? And a strong enemy unit only fights as if it had the strength of my weak unit?

Later it says:
"In continuing combat (melee), a unit with lower combat strength will be overlapped, so the higher combat strength unit fights with extra strength equivalent to half the difference between the units’ actual combat strengths."

To which value is this "extra strength" added? And what does overlapping mean? This is nowhere explained in the manual.

As I side note I need to mention that the manual doesn't make a great job in explaining how men numbers, unit strengths and POAs are used to calculate the real result of the fight. The FoG1 manual has at least a chapter which explains the combat calculation. Does such a thing exist for FoG2?

Thank you for any help!

Simply put, anytime a unit charges, the enemy unit is considered as counter-charging. The impact is when these two enemy units have charged each other and eventually meet. Only their first rows meet each other. To calculate the outcome of this impact, these rows are considered as being of the same number of men, even if there's a smaller unit. Then the fight turns into a succession of melees (one each turn) (1) and the bigger unit gets a logical advantage (due to its number of men).

(edit)
(1) More precisely : after the initial impact, there's, of course, one melee with an intermediate outcome per turn.