My understanding is he could see the numbers but failed to recognize or make sense of these pictures.He wasn’t aware of the letter pictures anymore and could no

My understanding is he could see the numbers but failed to recognize or make sense of these pictures.He wasn’t aware of the letter pictures anymore and could not associate them with the “numerical symbols” stored in his memory (if our brains do it this way). But with the stored symbols he still can do mental math so his higher cognitive function must be at least partly intact. Using the computer program metaphor we can say his input routine for numbers is scrambled but the other calculation routines remained intact. My guest is because we do math, our brain create the association for not only the numbers but also what we do with these numbers (maths routines). And because we don’t work with numbers all the time (we also can do symbolic maths), it’s necessary to separate the numbers with its meaning to accomplish these feats. If I would “program” our brain, it’ll be much more efficient to separate the recognition routines with the higher-function routines because we need to adjust the recognition routines all the time due the (slightly) different fonts and hand scripts of all the people.