This pattern is what we like to call the '1231 2342' pattern, which refers to the scale degrees. Listen to this scale a few times to get it in your head, then play along with the tab to internalize it on your instrument. This particular tab starts you on the lowest note of the mandolin so you can achieve the full range of the C scale in first position.
This pattern's scale degrees look like this - 13 24 35, etc. You start by going up a third and then you go down a 2nd and it continues in this fashion. Just like the 12312342 pattern, listen to this one to get it in your head before jumping into the tab.