Besieging Forts - Reduction/Repair Formulas

[Mysterio]

Since I wasn't seeing the expected results in a game I'm playing, I thought I would conduct a test to confirm the formulas in the manual for Reduction Strength and Repair Strength during a siege were correct. Based on my test, they aren't.

TEST SETUP

1 High Priest (Strength 9) in Fortified City (Defense Value 250) being besieged by 1 Great Hawk (Strength 11, Flying) and 20 Black Hawks (Strength 5, Flying). According to the manual:

Repair Strength for the High Priest = 9x9/100 = 0.81
Reduction Strength for the Great Hawk = (11x11/100)+1 (for flying) = 2.21
Reduction Strength for the 20 Black Hawks = [(5x5/100)+1 (for flying)]x20 = 25

Total Repair Strength = 0.81
Total Reduction Strength = 27.21
Difference = 26.4

Therefore, the Defense Value of the Fortified City should be reduced by 26.4 from 250 to 224 when the Great Hawk and Black Hawks enter the province. But it's only being reduced by 6 (from 250 to 244).

What are the correct formulas?