Does UPS Track Growing Equipment???

I bought a 400w hps kit with some mylar and a timer. When I checked the weight that ups had it said 4.20. Wouldn't that be 4 pounds 20 ounces?? If so there is 16 ounces in a pound so how come they just didn't put 5 pounds 4 ounces?? Or is it 4 pounds 20 grams??? I thinks its a tracking code for pot growing equipment. AM I PARANOID???