Dear Ms. Caldwell,
Thank you for posting your request on History Hub!
We suggest that you review the U.S Census Instructions for the Eighth Census (1860), especially pages 17-19, for clarification about how slaves were accounted for. According to the instructions, “under heading 6 - Fugitives, insert, in figures, opposite the name of the owner, a mark or number designating the fugitives who, having escaped within the year, have not been returned to their owners.” Therefore, the number 54 for your ancestor may refer to his or her numerical designation and was among those persons who were fugitives of the state that had escaped and not returned.
You may wish to search NARA’s African American Heritage and the Library of Congress Slavery for research tips and resources; and the Slaveholders and African Americans 1860-1870 website for additional information and/or resources.
We hope this is helpful. Best of luck with your family research!