Sometimes CX allows 86H/K to be booked in advance, and other times they hold those two for airport check-in or high level MPO/OW status flyers. 86A/C in theory is ONLY give to high level MPO and OW members. They should assign you 86A/C though if your OW Emerald number is in the booking. 86H and 86K have less leg room than 86A/C but still more than the rest of the J seats.