bill - your jerky will be dry and leathery on the outside. on the inside, it will be dried to the level that you prefer. also, if you take a slice of jerky and twist it, it should be flexible, not brittle.
i prefer my jerky to be pretty dry, but some prefer it to be quite moist inside, almost like kippered beef rather than jerky. try for something in the middle and see how you like it, then go from there.
the temperature of your dehydrator shouldn't be above 140 degrees, so there shouldn't be any danger of overcooking them. overDRYING them, however, might be another matter, depending on your preference.