Earliest date for eligibility of ILR

[Aniqaanjum]

Hello
I have a question about how early I can apply for indefinite leave to remain.
I have skilled worker visa ( Health and care ) (extended from Tier 2 general) . I am unsure when is the earliest date I can apply for ILR as this is very important to me.

I was 1st granted a Tier 2 general visa on 08/ OCT/ 2017 but I entered the UK for the first time on a Tier 2 general visa on 20 OCT 2017 (12 days after the Tier 2 visa was granted) . As i have continuous residence since then therefore my five years for qualifying for ILR is in OCT 2022 . However, according to the rules of ILR I can apply 28 days before the qualifying period . I am not sure from what time "these 28 days before the qualifying period" is calculated from ? Is it calculated backwards FROM THE TIME OF TIER 2 VISA granted ( 08/OCT/2022) OR FROM THE TIME I FIRST ENTERED UK PHYSICALLY ON 20/OCT 2022 ?
I want to apply as soon as possible but I am afraid if I submit application by counting back from date of grant of 1st time Tier2 visa will my ILR application can be rejected ?
Please advice
Thank you

[zimba]

The qualifying period starts from the first visa issue date