Section 400 is on the highest level of seating on the right side of the venue when looking from the stage. This section is close to the middle of the 400 level of this side of the stadium, so there should be a clear view of the stage even though you're on the upper level.
Row B is the second row in this section so it is one of the best places to sit in this section.
There are 20 seats in this section and when looking at the stage, Seat 1 is on the left side of the section. This means that Seat 12 is closer to the right side of the section, nearest Section 401, but is closest to the middle of the section.