Newbie totally confused by jacket spuds!

Hi all I joined WW last Thurs and am confused already!!
Can someone please clarify for me the points in jacket potatoes? Went to class and the leader scared us all half to death telling us an average size potato is worth 8 propoints! Had one for tea and it weighed 150g raw and after it was cooked it weighed 100g... I put this as 5 pp as couldnt decide if it should be 4 or 6! the Pocket Guide says if you cook potato at home use the raw potato weights given (which would be 3 pp for 150g potato) and then the book says 'however if you need to know the pp value of a ready baked potato then 100g potato is 4pp.
So should i have pointed 3 points as it was a home baked potato?
HELP!!!!

Hi you are right to point the potato at 3 ProPoints..

That's good, thanks for clarifying that for me it means i've had less propoints than i thought, YEY!! Now, where's the biscuits?!