Without access to a Samsung SL-M2020 printer, I have to base my information upon information in the manual and on HP's support pages.
According to page 130 in the manual (http://h10032.www1.hp.com/ctg/Manual/c05790048.pdf#G12.4667466), the setting for 2600 m would be level 3 = "High 2".
No details appear on page 153 (Device Settings), so I guess that you will have to install the Samsung Easy Printer Manager software (links in my previous message), and check whether anything inside explains how to set the altitude. Unfortunately this seems to require an older Mac or a Windows PC.