OK, fair enough. I will rephrase: I don't see any plausible mechanism by which you could know this, though I do concede that there are some possibilities. Maybe you have ESP. Maybe you have access to secret alien brain scanning technology. Maybe you hired a private investigator to suss out the depth of my understanding of the subtle and complex differences between belief and knowledge (though how he might have done this without my being aware of it remains a bit of a mystery). I have no idea. So yes, it's possible that you have some basis for believing that I "do not have a deep understanding of the subtle and complex differences between belief and knowledge". It's also possible that the earth is flat. But if you want me to take either possibility seriously then the burden is on you to explain it to me. Until you do that, the most plausible explanation I have for your behavior, and the one I am now going to start acting on, is that you are simply a troll.
Of course you know things I don't. Everyone over the age of 2 probably knows things I don't. Why would you even ask such a stupid question with such an obvious answer? And why did you phrase it in such a pretentious way? "Possess knowledge that you do not" -- who talks like that?
Does this have any affect on your belief that "so you cannot possibly have any basis for assessing my understanding or lack thereof" is a true statement?