Hi Cath
Depends where you were post prandially speaking. Had you eaten a slow release low carb meal, that might have raised your levels a little later than expected - as some of the LOW GI foods do?
Exercise can sometimes temporarily raise levels - but they then go down again fairly quickly if you don't eat anything before re testing.
You are not alone in your confusion! The rules, such as they are, are always changing and everything is very individual - for example in a book I have called Diabetes the First year by Gretchen Becker, she uses a phrase whenever she is giving advice - "Your mileage may vary" which she shortens to YMMV on almost every topic related to diabetes!
I think the release of sugar into the blood stream varies with the kind of exercise you are doing. It has definitely gone up for me sometimes, before dropping nicely an hour or so later.
Cathy N