here in that mod there it is explained , also with pictures https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2187317913&searchtext=Doubleticketdesk

I know , thats why you also need the staff mod , and there the staff mod desk , then you place the arrow at the second staff position , then you can hire a second staff. That is the only way at moment , because the game not allows it the normal way

The double ticket desk only allows 1 staff member to work even when u set it to 2