Can you tell us the name of the kit? Was it ordered on-line or purchased in a store?
If you're using a kit, it should have a set of instructions inside. Can you tell us what your instructions say regarding the ingredients? What we're looking for is water volumes, total amount of malt extract (cans are often 3.3 Lbs, many kits come with two cans, for example), and the boiling instructions.
If the water volumes are off, the OG will likely not be what was expected, as MaltLicker mentioned.