Okay, let me try and break it down:
1. Technically speaking, a petitioner is supposed to file the month their CN becomes current. So in your DIL's case if her CN is below the number listed for November, that means she's current in November and her AOS package is eligible for acceptance by USCIS from Nov. 1st.
2. However because she probably wouldn't be scheduled for an interview in November if her case file is received in Nov, and because AOS process takes a bit longer to get adjudicated compared to CP, it is possible for one to send in the AOS package up to two months in advance of their actual current month. This means if your DIL's CN is current in November she could send in her AOS package as from Sept.
3. The last sentence you seem hung on is a 'disclosure' - it points out the possibility of the package being rejected or the petition being denied due to early filing. That is because some FOs have chosen to not recognize the memo that allows for early filing and they are treating cases filed prior to the month the CN becomes current as improperly filed, while other FOs don't have any problem with such. So at the end of the day, the spreadsheet is basically asking each person to weigh and decide on their own if they are willing to take the risk of filing early with the possibility of gaining some time, or simply wait until the month CN becomes current and only file then as this gives them the peace of mind their petition will not be denied on the grounds of early filing.