If the altitude is on the label, write the value and the unit, separated by a space (e.g. 1500 m).
Sometimes, altitude appears in a range of values, e.g. between 1000 and 1500 m. In this case it should be added as 1000-1500 m.
Sometimes there is an apostrophe after the number, which means "feet" (ex .: 1000 '). In such cases, should be submited the unit ft (eg, 1000 ft).
If altitude is not specified, there is no need to deduct it.