My ancestors were astute enough to know that they have also 10 toes and they used a base 20 system that survived a little in my language and in the collective culture.
For example, there is a hospital in Paris called les quinze-vingts (the 15-20) because it hosted 300 patients when it was created during the Middle Ages.
Another example : 80 = quatre-vingt = 4-20 literally.
English used to use a similar scheme -- even now, four score is understood to mean eighty as used in the Gettysburg Address. Score is an archaic word for twenty from a tally mark that was recorded when counting things (probably livestock).
Do the Belgians and Swiss still use septante, huitante/octante, and nonante instead of soixante-dix, quatre-vingts, and quatre-vingt-dix? That system never caught on in France though...
Regarding the hundreds chart, I think it would be more effective if the numbers were right-justified in the cells so the cycling over the digits would be more obvious.