I think this is a "phantom" index entry

Name: Mary Rickards Brain
Year of Registration: 1839
Quarter of Registration: Jul-Aug-Sep
District: Chepstow
County: Gloucestershire, Monmouthshire
Volume: 26
Page: 62

where as this is the real entry

Name: Mary Rickards Rickards
Year of Registration: 1839
Quarter of Registration: Jul-Aug-Sep
District: Chepstow
County: Gloucestershire, Monmouthshire
Volume: 26
Page: 62

If you have access to the images check them out.

If it is a phantom its probably a submission by a researcher.