I agree with Rob, it's probably only means something to the Ancestry member who originally put it there. I doubt it's military, since it's on both Amasa and his wife.
For what it's worth, we're looking at Illinois in the 19th century. Amasa Lankton died in Illinois, and probably came from New York:
Find A Grave, database and images (
https://www.findagrave.com : accessed
28 April 2019), memorial page for Amasa Lankton (1789–21 Nov 1857), Find A Grave Memorial no.
89590492, citing North Kingston Cemetery, Genoa, DeKalb County, Illinois, USA ; Maintained by RobMinteer57 (contributor
47389024).
"Illinois State Census, 1855," database with images,
FamilySearch (
https://familysearch.org/ark:/61903/1:1:61QZ-JMM : 11 March 2018), Amasa Lankton, Kingston, DeKalb, Illinois; citing Kingston, DeKalb, Illinois, 3, p. 59, Illinois State Archives, Springfield; FHL microfilm.
"United States Census, 1840," database with images,
FamilySearch (
https://familysearch.org/ark:/61903/1:1:XHYW-R6X : 15 August 2017), Amasa Lankton, Hinsdale, Cattaraugus, New York, United States; citing p. 44, NARA microfilm publication M704, (Washington D.C.: National Archives and Records Administration, n.d.), roll 267; FHL microfilm 17,180.
"United States Census, 1820," database with images,
FamilySearch (
https://familysearch.org/ark:/61903/1:1:XHLB-GBL : accessed 28 April 2019), Amasa Lankton, Aurora, Niagara, New York, United States; citing p. , NARA microfilm publication M33, (Washington D.C.: National Archives and Records Administration, n.d.), roll 69; FHL microfilm 193,724.