@Tod ********
From my experience this is not the case - the rule states "at least 3 months after being granted permission" which means the date you go in and apply and receive your extension. I have always clarified the date you can go below 800k with immigration officer and it is 3 months after the applied date in your passport. Another way to look at it is you need to be at 800k for 5 consecutive months - 2 before and 3 after.