It does take quite a bit of chocolate, I think. Years ago, my kids had a fund raiser at school and had brought home the goodies that friends and relatives had bought. Most of these 'goodies' were wrapping paper and non-edibles, but my brother had ordered chocolate covered raisins.
These were in a theatre-sized box with cellophane wrapping inside a closed box with all the other items ordered. Our 25 lb. Pug managed to get into the large box, find the choc. covered raising, tear into that, and eat the whole thing while we were gone.
He was quite miserable afterward, but he didn't end up having to go to the vet (at the time I didn't even know chocolate was toxic to dogs), and he lived many, many years after that. He did throw up quite several times, and he stayed stretched out on the cool tile in a quite corner for about 8 hours.
It ended up that my brother donated that $7 to the school and never received his chocolate!! My kids never heard the end of that!! Of course, he would rather tease them about it forever than take the $7 back.