You always export at 1:1. All depends of pixelation you set.
If you have a 4 pixelations for H/w and the image is 512x512, the exported image will be 128x128, due 512/4= 128. So exports at 1:1 to be ready to use, in games or whatever, so you not need to resize, that all people requested so i made in this way.
And yes to zoom only works with mouse wheel sorry.