He highlighted your sentence asking why they didn't have football in the leaving cert when you were taking it. Then he suggested that admitting to being a Fingal fan would result in you failing such an exam, a somewhat clumsy jibe about your (ex-)club. Your reply casts some doubt on your result in English too.
Just in case it helps, here's a short glossary to help you interpret bluewhitearmy's post.
Tbf: A common internet acronym for the phrase "To be fair".
ya: Limerick scum dialect for you (singular).
English comprehension aside, I haven't seen these Cann tables before. It's interesting to compare the English and Scottish tables. We should be careful not to compare the current Irish one with those two though, as we're much earlier in our season. I might hack together last year's LoI table as a Cann table tomorrow, if no one beats me to it.