PBS Dependant ILR date

Hello, can you please help with the exact date my PBS dependant can apply for ILR?

I am aware it is 28 days before 5 years of full residence, but what day should I count as starting date?

1. Visa (in her passport) was issued on 10.11.2017.
2. She entered UK on 15.11.2017.
3. Her first BRP starts from 26.11.2017.

Which date out of these three should be start of 5 years?

Thanks!

Option 1

Thanks. And from that date we can retract 28 days, so she can apply for example on 15th of October 2022?

Yes