1.5.7c
few plugins (don't think list is relevant to question, in case please let me know)

First time trying to use attributes, and read the docs, and made some local tests, what I am missing is how to have the ability to choose multiple quantity.

e.g.

Product > box
Attribute > size
Sizes > small, medium, large

Customer should be able to select i.e.
1 small box, add it, and that's no issue
but what if s/he wants
1 small
3 medium
2 large
for a total of 6 boxes

How would I set this up?

Thank you