How much information do I have to provide in the 'Description' box?

Just type in as much information as you think we will need to answer your particular question or query. Brevity is usually a good attribute to have in such communications but not if it leaves out lots of relevant details related to a complicated issue. Extensive, descriptive information can also be good thing but not if it buries your simple question under a mountain of irrelevant details. In either case, too much or not enough information may delay a response to your ticket so try to steer a middle course when you write your description.