I wonder. Let me ask some of my coworkers who have seen shows in Saitama. maybe they know. It could be that arena b is the surrounding seats, not those on the arena floor or it could be that is your entrance. I saw a concert at Osaka Dome and my seat number was 4-s-58 which I thought was a strange number. The first 4 turned out to be the door I had to enter through. My ticket for utada at Osaka Jo Hall says I am in A-1X-XX (Just don't want to jeapordize my seat if I am breaking any laws or something) But I gather that means section A, row 1X seat XX. Do you live in Saitama?