This was likely (look at the card and it should say) that it was from a company muster roll. They usually put this in the remarks column to give the reason for his being absent. The cards were extracts from original documents that are at the National Archives unless as in the case of many of the officers, original documents were microfilmed to the CMRS too.
I hope this helps.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment