The way I read the UK website is - my flight leaves ATL at 10 pm, but I connected from a 4:40 pm flight on a Sunday. I’d like to schedule my PCR test Thursday morning to make sure I have the results. Technically from the UK website 3 days would include Thursday. I’m assuming they dont adjust the 10 pm US flight time to 3 am Monday.
I think I’m ok, but guess I’d like opinions