I have a relative on the Indian Census Records on Ancestry.com please help...?

The information is available through the National Archives. If you type "Chickasaw Freedmen, Census Card #: 251, Dawes' Roll #: 990." into the search engine there are at least 3-5 sites that come up. Also the Chickasaw Tribal site should have information that would be helpful. Ancestry does not appear to have copies of the actual census cards available, only indexes.