Unit fortification value discrepancy

[MAS]

I'm playing v1.01.09 and think I've found a problem, or at least I don't understand it after reading the manual.

2 rifle divisions have just arrived on map from reserves, to the same location. They both have virtually the same to&e, fatigue and experience levels, all within 1-2% of each other, but one has a construction value of 20, while the other is 8.

I thought I had found the reason when reading under rule 21.2.1 that "Construction values are also reduced
based on the supply level of the unit. In no event will they be reduced below 20 percent of normal due to supply level."

Here are the units: 251st rifle division has 21% supplies and a construction value of 8. 249th rifle division has 50% supplies and a value of 20. But 8 is 60% less than 20, not 20%, so that violates the above.

Am I missing something, or is this possibly a bug?

[Yogol]

Maybe the normal construction value of both units is 40. Then, you take supply into account.

20% of 40 is 8 (CV of 251st).
50% of 40 is 20 (CV of 249th)

(but it can not fall below 8 (20% of 40))