I have known for years that I have trouble distinguishing between, say, "430", "43,000", and "340,000" -- they are all threes and fours and zeroes, the order has no particular meaning to me unless I concentrate. Too many consecutive numbers and my mind just glazes over. It makes budget work tough. My interns do math in their heads, and they know they to carefully check any figures in documents I build -- just as I have to check their work for political correctness and appropriate phrasing for a given audience.
Still, there is a separate skill I have heard called "spatial-numeric ability" at which I excel -- I am very good at those tests where you choose which shape will result upon folding up an oddly-shaped piece of paper with markings here and there -- something that I have applied in costumery and woodworking, among other areas. I made my own patterns for stuffed animals and clothing since I was about ten or eleven. It also lets me judge readily whether one item will fit inside or mesh with another -- helps in packing cars, fitting chicken pieces into a pan, or solving picture puzzles. I seem to recall reading somewhere that this trait is inherited father to daughter, mother to son, and cetainly my dad had it but my mom emphatically does not.