I see that the documents posted in your query are a claimant affidavit and an extracted military service detailed muster sheet from a compiled military service record. So to answer your questions, I needed to locate some more documents.
While searching for military service records, I was able to locate several documents. The Ancestry.com U.S. Civil War Soldier Records and Profiles, 1861-1865 database transcript for Milton Howard displays his enlistment date as January 21, 1864 under the rank of Private with the United States Colored Troops (USCT). The document provides a descriptive service record indicating that Milton Howard served in the 60th Infantry Regiment, Company F. His record shows that he served from February 11, 1864 and “mustered out” on October 15, 1865 at Devall’s Bluff Arkansas, USA. The source for the aforementioned record comes from the Roster & Records of Iowa Soldiers in the War of the Rebellion. Please find attached images of the transcript
I also recommend a close examination of the 1910 U.S. Federal Census for Davenport City, Scott County, state of Iowa-Milton and Lena Howard household. The following enumeration specifics can be drawn this original document.
Enumeration Sheet Number 3A
Enumeration District (ED) Number 0144
Enumeration Date: April 16, 1910
Enumeration Line Number 4
Enumeration Column Number 3 (Q. Name of each person of abode on April 15, 1910
was in this family, A. Milton Howard)
Enumeration Column Number 30 (Q. Whether a survivor of the Union or Confederate
Army or Navy, A. 2-)
The (2-) notation represents Milton Howard’s service of less than 2 years with the union army. Please find attached the Ancestry.com database transcript, the image of the 1910 US Federal Census record enumerating the Milton and Lena Howard household and a blank 1910 U.S. Federal Census form. The source is the Ancestry.com database containing digitized collections from the National Archives and Records Administration (NARA) microfilm collection.