So I've heard chocolate is bad for dogs and such...but how much do they need to eat before it's harmful?

While I was out, Josie got on my table and ate half a chocolate orange and 3-4 timbits (not sure if the US has Tim Hortons or not...but timbits are like bite sized donuts...I think there was a chocolate one, a powdered filling one and something else...) Do you think that is enough to harm her? What would I look for if something were to happen? I know I'm probably paranoid, but I'd like to know just in case....

Needless to say...Josie is going to bed without her supper....I don't think she needs anything after eating that!