Thanks everyone, I felt really daft, I had all the guidance, but just couldn't work out how to count the 20 days. I am on a very tight time arrangement, as I need to get the sow home and some young pigs away, then bring a young boar on to go into isolation with some gilts to get on a ferry to Ireland on 5th December, my brain is going to be totally scrambled by then. I have a one day window for 'offs'!