Welcome to the forum.
I have a Bradley digital thermometer, and it can not be calibrated. If it is reading 13°C higher using the ice bath method; as Grouperman941 mentioned use the boiling water test. If you don't have enough ice, not letting the ice water sit long enough, and don't swirl the probe; you won't get an accurate reading. For the most accurate boiling water test it is best to calculate the altitude, and barometric pressure (if you now it). Boiling Point Calculator
If it is reading no more than 4°C, I would guess you could just compensate by adding, but there is a member who is a scientist, and I believe he once noted that as the temperature increases the difference in the readings will be exponential, as the temperature increases. For example, 13°C at 0°C, may be a difference of 30°C at 107°C. So if it is reading that far off, and it is new, return it for a new one.
One other thought. A low battery can cause an error in the reading. If it is beyond warranty, and the probe is bad, you may be better off buying a new digital probe thermometer, rather than paying to replace the probe.