When am I eligible to apply for ILR earliest?

Hello there, I'm hoping to get some clarity as to when the earliest date is for me to apply for ILR. 28 days prior to what date?

The letter I received says Sep 21 2020; the vignette says Sep 21 2020; I entered the UK Sep 27 2020. But the BRP says issued on Sep 7 2020.

When am I safe to apply for ILR?

Thanks.

Earliest date of ILR eligibility is Sep 7 2020 + 5 years - 28 days.

Read: Applicants can benefit from the date of the ILR decision