The figures quoted for non diabetics are less than 7.8 after a meal?
And yes, non diabetics' blood sugars do go up and down, normally in the 4 to 7.8 range, though they do sometimes go lower (no need to fear hypos) and a bit higher if they pack on the carbs.
The phrase diabetes is a marathon not a sprint comes to mind. Different people have different tolerances to carbs - some people can reduce their levels to non diabetic by a relatively small adjustment to diet, others have to go practically keto. Some people can tolerate the carbs in some foods, but not others. Your meter will tell you what you can tolerate, but bear in mind that the manufacturers don't guarantee it to be absolutely accurate - a reading of 8 on one meter could be 7 or 9 on different ones. (Plus it's easy to introduce error through lack of hand washing). Then there's the fact that stress and illness can raise blood sugar, irrespective of what you're eating.
I'd be much more concerned with trends than a single reading. You sound like you have pulled your readings down into non diabetic territory, even with the odd blip. (Many T2s find porridge problematic). Hopefully with some experience you'll be able to back up on the testing. It tells you how your body reacts to different foods, but once you've learnt this you should be able to test much less.... No need for self flagellation over one potentially slightly errant reading
Good luck.