First time BA traveler, normally DL business class international but this flight suits my schedule so here I am. I am choosing my seat online and got to the LHR-LAX leg and the seating chart shows a 1-2-1 arrangement, listed as a 777 -300ER but every other seating chart I see for the BA 777 looks nothing like this. Am I in another dimension?

Seats are numbered 5 through 15, A,D,G and J.