Sigil metadata code questions

I was wondering if someone could tell me if I have the metadata code right for ISBN:

<dc:identifier opf:scheme="ISBN">9780996357029</dc:identifier>


and does anyone know what this one is: It doesn't show up in the metadata editor window, just the content.opf file

<dc:identifier id="BookId" opf:scheme="UUID">urn:uuid:98ae0034-7473-4ebe-b39d-809952f0b9e3</dc:identifier>


Thank you,
Ava