I think the "box sizes" really only describe the default selection — an approximation of how much they put in your cart before you shop. I think I usually swap out at least half of what's pre-populated.
As for individual items, I probably haven't ever checked weights because they're not in the email confirmation — which is what I usually use to check if I've gotten everything. The weights are only on the web purchase history.
Everything from this week looks fine, but most of what we ordered was by count, rather than by weight — or prepackaged. (The 3lb bag of Bartlett pears for $4 was a nice find — they're really tasty.)