Starting with the repository, its name could be “Archdiocese of Saint Louis Archives” with its address as recorded on the document; “20 Archbishop May Drive, Saint Louis, MO 63119”.
The RootsMagic baptism master source allows for a source name, church and location. The source name could be “Certified copy of baptism certificate”, the church is “St. Joseph Lithuanian” and “Saint Louis, MO” as its location. The church details and its location are stored in separate fields in the source master.
I am not sure what the number (314.792.7020) is at footer of document and I assume the ledger number 22-11 is the internal document number for this template as used by the Archives of Archdiocese of Saint Louis.
I would probably have a citation as “Archdiocese of Saint Louis Archives; St. Joseph Lithuanian Baptism Register; Seal Date: 5/14/2012; Rev. M.A. Vitkus” but up to you. This style of citation is similar to my London Archive baptism records from Ancestry so I would mimic their style (but they add a reference number). If you have other baptism records, I would suggest to use a similar style to them.
As an aside, the Evidence Explained book previously mentioned covers “Church Books: Named/Numbered Volume Archived Off-site” page 312-3 maybe also be useful. In essence, this covers your scenario of the baptism register of St. Joseph Lithuanian being archived at the Archdiocese of Saint Louis Archives.