Why Purchasing is not using the Manufacturing Calendar when calculating the receipt early days?

1. I have setup the Receiving Options to Receip Days Early = 5 days and Warning.

2. The organization has attached a Manufacturing calendar (4/4/5) with days offs and holidays

3. The promise day for the PO# is 8/27 and we are doing the receiving today 8/20. Why are we receivintg the days early warning? if we count 8/21, 8/22, 8/23, 8/24 and 8/27 should be the only counted days and not 8/25 and 8/26 as they are days off

Is Purchasing taking weekends and holidays when calculating days early?

Thanks,

Iliana