ICAO codes for different versions of the aircraft.
https://en.wikipedia.org/wiki/Boeing_777
772 = 777-200
773 = 777-300
77W = 777-300ER
Don't think the seat map is specific to only that abbr. The airlines have control over the seat arrangement, so knowing 77W and KE should be sufficient.
Never heard of 77I, but the 77L is a 777-200LR. Hopefully someone with more knowledge will reply.