Ahah, so expanding upon things to get to “total” Movement Penalties vs just Encumbrance ones is where you start adding Minimum Maneuver Penalties from maxing out one’s skill Man. In Armour, “leftover” Strength bonuses, etc.
The example on 144 doesn’t show -30 but -10 for the dead weight Encumbrance penalty.
Are you asking, if it were -30 instead?
Ahah, Pg 143 is the 20’ / round example.
So it looks like they are using the -20 from a 2-3x weight penalty vs a 3-4x one.
This is correct because, as you say, 22lbs. is = to 0x to 1x, up to 44lbs. is 1x to 2x, up to 66lbs. is 2x - 3x.
Then the key factor is they’re supposing you know about the Breastplate Min. maneuver Penalty of -10 in the example on Pg 144.