Updated.
"Airlines such as Lion Air that operate the 737 MAX9 with 221 seats need another exit row, so the plane was designed to accommodate that. That exit row door has a portal window.
Alaska operates the plane type with 178 seats, as does IcelandAir, while United operates it with 179 seats, so they don’t need the extra exit rows."
How in the world are two airlines able to have a difference of 43 seats on a plane like that?