Yes Peter that's a great document wrt the history of the Baptist Chapel, I think iot's already within this site's Resources somewhere.

Re the register/records used to support the GlosBMD database, I can only suggest contacting the various parties reponsiable for that website, namely;

"Gloucestershire Registration Service and Gloucestershire Archives
in conjunction with Gloucestershire Family History Society"

See links on this page http://ww3.gloucestershire.gov.uk/bmd/MainMenu.aspx

Hopefully they can clarify where there information came from.

Suggest Glos Archives as first port of call ?
https://www.gloucestershire.gov.uk/archives/plan-your-visit/where-we-are-contact-us/