NHS app alert, Tuesday or wednesday?

[wantmorenow]

just got alert that I need to self-isolate for 8 days.
Does that mean I was "pinged" as being in contact with positive case Tuesday or Wednesday ?
cheers.

I’d say Tuesday as contact day is day 0 - does it matter though?

It would help understand where the ping came from. I dropped some gifts to a relative on Wednesday and had a chat from their path whilst they were in their porch (about them feeling rough and to wave to their 9 month old whom I've hardly seen due to covid) and they tested positive today from a swab on Wednesday. I know I couldn't have been at risk from that as I had mask, was outdoors and they were inside.

Tuesday I did a supermarket shop and staffed car wash only so maybe more at risk as was indoors with others during shop.

I have had so little contact with others it's purely curiosity .