Morale adjusted power

The manual says "At maximum morale they deal their full damage which decreases in a linear fashion with sinking morale (up until 55% morale - after that, damage is not reduced further)." I assume unit morale is 100 * HP / HP_MAX. This would suggest that dmg = base_dmg * (0.55 + 0.45 * HP / HP_MAX). However, the power shown for infantry seems to be reflecting a linear dmg increase starting at 5.5% instead of 55%. As you can see below the attack and defense power of these 10 infantry are 27.1 and 33.9. We can do the calculations for 55% vs 5.5% as follows (Just doing defense (5 dmg) to demonstrate

10 * 5 * (0.55 + 0.45*132/200) = 42.35

10 * 5 * (0.055 + 0.945*132/200) = 33.935

As you can see, the displayed value matches the 5.5% equation. Is this a bug in the UI display or is the manual incorrect? Or am I missing something?