The temptation is always to think that Ancestry.com is wrong. That's not the way it is.
The image on this post comes from the 1870 Census for Hancock County, Illinois. For some reason, some of the townships are listed in the census with their Congressional township numbers instead of their civil township names--like the one where this ancestor was located--Township 3 North Range 8 West--Walker Township.
The screen shot clearly indicates this township as 3N 9W. The family should have been in Walker Township in 1870 as the father purchsed a farm there in the 1860s and did not sell it until the 1870s.
Ancestry in its headings, indicates it is Township 3N R 8W--the enumerator indicates it is 3N 9W. When I viewed the pages before and after, those pages were titled by the enumerator correctly and the other information on the pages matched. It looks like one error by the enumerator.
Always look before and after and do not assume Ancestry.com made a mistake.
The real question is how to cite this census for the issue of Casefile Clues in which it will be referenced.