ILR query – extension & 28 days early

Hi,
I first came to UK on 10/09/2015 and had a Tier 4 visa from 2021-2024. I extended my Tier 4 visa on 12/09/2024.
It is said in the long residence caseworker guidance that ‘the applicant must also been on their current immigration route for at least 12 months.’ It is also said that ‘applications being considered 28 days or less before the required qualifying period is completed’ can be granted.

I wonder what is the earliest day that I can make an ILR application via the 10-year route.
Is it 28 days before 10/09/2025, or 28 days before 12/09/2025, or any other dates?
Thank you very much for your help!

The date of entry is no longer relevant.

Read: Lawful and continuous residence changes to Long Residence route from 11 April 2024

Also read: Applicants can benefit from the date of the ILR decision