Ancestry.co.uk was my source. It has "Holyhead" as a sub-registration district (of the registration district of the Isle of Man) that covers Malew, Santan and parts of Braddan and Marown. For some reason the range of sub-registration districts for the Isle of Man is: A-F, Holyhead, H - indicating Holyhead was used in place of "G" for some reason.

This is the info provided on ancestry regarding sub-registration districts:
"Occasionally, counties will contain parishes with the same name or a large parish might include multiple instances of an Enumeration District number. Sub-registration districts, which are a related to civil registration districts, are then used to distinguish which parish or part of a parish is referenced."

I don't know any more than that but would be happy to find out what it all means.

Ruth