Personally I'd be inclined to believe what's written inside the hydrometer rather than what's written on the scrap of paper they included with it... But it's in your best interests to check your hydrometer in distilled water anyway, so that you know if it's got any kind of inherent inaccuracy (in addition to any caused by temperature) that you need to calibrate out when taking readings - the 'calibration temperature' specified doesn't do you much good if it's not actually accurately calibrated at that temperature! If it does have an offset, you could just make yourself a new calibration table to include both the temperature calibration, and the offset.