The first element in the formula for First Charge Intensity is "Opening Army Intensity (20)".

Does that mean the greater of the opening army intensity or 20? According to page 19 of the BoB2E, opening army intensity is equal to [20 + starting conditions + battle events]. It's not fixed at 20.

What am I missing here?

The first element in the formula for First Charge Intensity is "Opening Army Intensity (20)".
Does that mean the greater of the opening army intensity or 20? According to page 19 of the BoB2E, opening army intensity is equal to [20 + starting conditions + battle events]. It's not fixed at 20.
What am I missing here?

Nothing, I think

BoB2, page 17
All battles start at Army Intensity 20, modified by
Starting Conditions and a random Battle Event.

Then the various modifiers are added

Ah, gotcha.

Thanks!