Private First Class Cecelia Glass here is a clerk –an “Administrative Specialist”–, which is called a 71-Lima in the year 2003, when this story takes place.
A “71-Lima” is the alpha-numeric code given for “M.O.S”, or “Mission Occupational Specialty”– your official job in the Army. Cecelia Glass has been to all the most recent “71 Lima” schools and so she is actually in a position to know more about the latest administrative software than Staff-Sergeant Ransom, who actually outranks her. It is common for a younger soldier to have “the latest” updates to training, so they may be in the position to train older soldiers on new upgrades, which is what is happening here.
Every MOS (pronounced by just saying the letters out loud: “Emm-Oh-Ess”; no one ever calls it “moss”) has an alpha-numeric code assigned to it. Infantry is “11B” or “Eleven Bravo”, Engineers are “12B” or “Twelve Bravo”.