what is the best aspect ratio of screenshots

I got a note for my project as following :

  • Use the recommended screenshot resolution, as it is right now the screenshots are too big. (vertical: 460 x 900, horizontal: anything with an aspect ratio of 16:9)

but (vertical: 460 x 900, horizontal) is very small for our screenshots … could you tell me what are options for a ratio of 16:9 ?

you can try to upload Preview Screenshots images with width not more than 800px.