There is a thing called dyscalculia, a form of dyslexia with numeracy skills. Reading is no problem, but understanding mathematical concepts are a real problem. I found out a bit late, but have developed strategies to cope...although avoiding anything to do with calculation is still the first option. Not as common as dyslexia, but one of my daughters, and her daughter have it too. Also a high amount of lefthandedness in our family too...me and 2 out of 4 kids.
Like those with dyslexia, we tend to end up in trades, not because we are stupid, far from it, but we think in 3D pictures, which is extremely useful in manual jobs. My daughter is a dressmaker, being able to see a 3D garment in her head is a bonus.
So ignore 3 pages of people putting down those with inadequate numeracy skills, I'm sure they are not perfect, but we won't make them feel bad about it.