While I was in university, I had all of the understanding of the information in my head, and I can orally explain things, but, if I tried to explain things long term in essay form (and social sciences is all essay writing) then my thoughts got lost, the directions changed and I always had comments like "abstract" "re-write" "too wordy" "re-phrase" etc.

In economics class....I understood the theories perfectly. When it came to the equations, I could do the numbers in my head but I kept picking the wrong formula for the equations. I used the formula for compound interest to figure out depreciation.

Not to worry too much, Mr V. We are our own worse critics (after professors lol)

You are still an intelligent human being who understands more than many other people. There will always be others who still have better days or more knowledge of a topic than we do. However, it does not negate the collection of knowledge we still have. Just because I did not choose the correct formula in the depreciation question, does not mean I do not understand Macroeconomics as a whole.