(8) Remembering ten of anything
This might have been part of the artist's explanation, since a statement that people have difficulty remembering ten things could have been proved by the observation that they have trouble remembering the Ten Commandments. A counter-argument could have been that people counted on their fingers both in Europe and New Spain so it shouldn't have been too difficult. Hands showing five fingers (or not) are mnemonics in several places in the triptych.