ASICSKid's Matflex 6 Grade School Wrestling Shoes

Asics lists a "k11" size, but amazon lists "11 big kid". are they the same thing? also seen "little kid" sizing. what's the deal?

I checked foot lenght and it measured as 7.5". What size I have to order if I want a little spare space for toes ( narrow feet) ?

My son is 8 and wears a size 3 shoe. What is the difference between little kid and big kid sizes?

My niece has a 9 inch foot and we want to get this shoe. asics 81 matflex 6 gs kid's wrestling shoes what size do we need to order?