I found the following on the government's archives website:

" * Service in Union or Confederate Army or Navy

o The 1910 census (column 30) indicates whether the person was a "survivor of the Union or Confederate Army or Navy." The answers are "UA" for Union Army, "UN" for Union Navy, "CA" for Confederate Army, and "CN" for Confederate Navy. These clues lead to military service and pension records; see Civil War Records and Confederate Pension Records for more information.

o A word of caution: On the 1910 census, columns 30-32 are often "overwritten" with numbers like 2-1-0-0 or 6-9-0-0. These numbers are not the answers for columns 30-32, but were data summaries used by Census Bureau tabulators in Washington, DC, to compile statistical data.

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After I read this, I went through the 1910 census for Avoyelles Parish and found that Amos Fisher was not noted as a Civil War veteran while a number of other residents were. Among those: Leon Langley, William H. Oliver, G.W. Pike and Dudley Curry. I think this supports E.H. Barman's theory that the Amos Fisher of the 8th Louisiana Cavalry was Amos Fisher, Jr., and not his son Amos Kendall Fisher.