I'll pretend I managed to keep up with all the info in this chapter
From what I can gather, it goes something like this:
Anri and Nobuo arrived first and met up and went to the roof to watch for people arriving.
Yuki shows up with Zero but can't get his wheelchair past the counter, so she left him to turn on the front doors. Anri and Nobuo saw her and Zero arrive from the roof, but shortly after Ryouko also arrives wearing a mask and hat so they don't know who brought Zero.
Anri and Nobuo go down and find Zero. Yuki hides and listens to them talk. They believe Zero is dead and decide to cover it up to avoid the meeting being cancelled. Yuki decides to let them handle it and continues hiding.
Anri stays on the roof to keep lookout while Nobuo goes to move Zero and make it look like he went through with it first. At this point most of the others are arriving. The last two being Mai and Meiko.
Mai and Meiko are 12 and 13, so Anri needs to check if who is a participant and who's an outsider. Mai is suspicious cause she was just sitting on the bench and Meiko cause she showed up last.
Anri confirms with Meiko and Mai has walked away so she thinks everything is ok and goes with Meiko down to the room as everyone gathers up. Yuki comes out of hiding and is the last to get her number and go to the basement.
The inconsistency is that previously Yuki claimed she was last to arrive and enter the building. Anri only went to check out Meiko cause she was the 13th person, so Meiko must have been the actual last person to show up. Apart from Anri and Nobuo who were doing their cover up, the only person with any reason to lie would be the person who brought in Zero, so it must be Yuki.