So usually when I put my hydrometer in my cylinder I can see the rim of the cylinder near the wort level. I am wondering if your hydrometer was floating when you took your reading? I plugged in your recipe values and got 1.080. You would have had to have boiled it down to 3.32 gallons to get the value you measured. DME is fairly consistent, so you can count on what kind of numbers it will put up. Something went wrong in your measurement or how much stuff i.e. water or ingredient measurement. Put your hydrometer in water and see what it reads. It should read pretty close to 1.000. If you have any DME left you could make a very accurate solution and use the online calculator on Brewers Friend to see if your hydrometer is reading correctly.