can i make export size like a rectangle?or it must be a square

hi~guys:)

in Substance 3D Painter,

i bake a texture and size is 2048x1024(rectangle)
but when i export texture,
it is look likes locked,must be a square (2048x2048)

how to change the export texture size,
make it like a rectangle (2048x1024)

i cant find the option :'(