For the YLISSB contests, you send signal report plus state (US) or province (VE) or country (everyone else) and if you are a Y>ISSB memeber, you send your member number. If you are not a member, you omit that last part.
So, I would send 599 MD, VE3KI would send 599 ON and G4PDQ would send 599 G. If any of us were members, we would add a member number.
If you work a member, write down their YLiSSB number in your log, they count extra - the scoring on this one is very complicated - full rules
here.
Always fun to hear the YLs calling CQ and give them a contact. Have fun!
73 John K3TN