Benjamin Rush, the “father of American psychiatry,” described the lightning-quick calculating ability of Thomas Fuller, who understood little math more complex than counting.
(Scientific American Mind;Volume 14, Number 1;Islands of Genius)
Can I say here "...who understood little about math more complex than counting."?
But the second example is a bit dubious 'Understand' has a special meaning in the case of languages. 'I understand Italian' means I understand what is said or written'. And 'I understand about Italian' is scarcely intelligible; perhaps it means 'I know about Italian' (which, as you know, does not mean the same as 'I know Italian').