how do people join locked xbox live partys?

[AngelOrtiz]

Some people have been joining my party when its locked and i didn't invite them. I don't understand this its suppose to be locked

 

[Unregistered]

If you just put your party on invite only it takes about 13 seconds to actually lock so if u put it on lock and 3 seconds later someone joins its because it hasnt locked yet also if someone in your party invited them