Sorry to be labouring this point, but I for one still don't understand how you would judge when "2 days" is up. It is easy with 48 hrs, I know what time I arrived therefore I know exactly when I need to have left by.
In the 2 examples
Sighted on eg 3pm Thu, 6pm Fri, 10am Sat --> 2 days
Sighted on eg 10am Thu, 6pm Fri, 5pm Sat --> 2 days
the first is less than 48 hrs and the second is more than 48 hrs, but I don't understand how that are both 2 days, you have been recorded on 3 days in both cases, so it seems that under the 2 day scheme both are not allowable. Does it describe somewhere how the calculation is done, and how you determine at what time you need to have left by in these 2 cases under the new scheme?
Just to put some reality behind this; a couple of times this year I have made the trip into Birmingham arriving at about 1pm on Thursday and left the 48 hr mooring at about 8am on the Saturday. That is legit under 48 hrs, but if the change was made to 2 days, it would seem that would not be allowable.