I had a conversation with a Customs agent after I had ticked No, but had written 'chocolates' on the back. He said I was ok, as I had declared it on the back and the chocolates were pre-packaged.

In my early days of international travel, I used to ask a lot of questions as I didn't want to unwittingly do anything wrong. After a couple of Customs agents told me I didn't have to check Yes for pre-packaged candy (but still had to declare it on the back), I stopped doing so and have not had any problems.

I've even been asked: "Do you have any food?" (box was checked No)

I answered: "Just the candy I declared on the back."

"Ok, thank you." was the response.

I don't work for Customs, so I can't definitively say this is the proper course of action, but it's been my experience.