Possible answers may lay 8n what you ate to get the 10 and what you did activity wise in those 3 hrs
on the odd occasion I’ve eaten something I really know better than to eat, ie something that sends me high. I have tested expecting an awful figure and it’s actually been lower than normal. I figured as I’m usually very low carb my body was “shocked” and overdid the insulin response taking me lower and I simply missed the high. Kind of like a one off reactive hypoglycaemia response.
also a decent walk or some heavy lifting will drop numbers quite quickly for many.