You didn't believe the part in the manual where is says that the scale was professionally factory calibrated before shipment?
According to the manual it says the scale will show you what the required calibration weight is to be. Not having one, I can only imagine that it must be the 50.00 that is shown to you by the LCD. But whether that is 50.00 lbs or 50.00 kg or 50.00 g or 50.00 ounces I wouldn't know. Maybe it depends on what measurement you have selected.
I don't think I'd fear putting a 50 lb weight on a scale that has a 65 lb limit. Hopefully it has over limit protection.