This isn't their place, so He Yiran obviously wasn't comfortable explaining, and she didn't ask any further.
The person who was just guiding them brought them to a doorway before turning and leaving, and at this doorway there were people guarding it too. The invitation was only a preliminary check to get through the door; once inside, the invitation had another use—verifying their identity again.
The worker at the door took He Yiran's invitation, scanned it using a machine in front of the computer, and with a beep, He Yiran's information popped up on the screen, matching her identity. The invitation's job was done here.
The person collected the invitation and asked, "Miss He, are these three here with you?"
"Yes."
The worker nodded and asked again, "Miss He, how many wristbands do you need?"
He Yiran thought for a moment and said, "Four."
The person hesitated and asked, not too sure, "Four?"
"Right, four."
