If the surname is obviously a surname, but the "middle" name could be either a natal name or a maiden name, put both given name and middle name in the first name field.
This is a point of ambiguity in the way BG has the database structured, so just get the name in the fields and it will sort out ok.
To illustate why we dont assume about those troubling "middle" names, for example if the stone reads:
Dorothy Craig Hansen Shepard, what could it mean?
Craig may be a given middle name (her mothers maiden name for example), or it might be her maiden name.
Hansen might be her maiden name or name of first husband;
Shepard could be name of first husband or a second husband.
Remember, do your best to be accurate and if you are in doubt you can always use the SKIP button.