At least 2 screenshots are required overall (Max 8 screenshots per type, Types include "Phone", "7-inch tablet" and "10-inch tablet”).
JPEG or 24-bit PNG (no alpha), Minimum dimension: 320px, Maximum dimension: 3840px, Sample sizes: 320 x 480, 480 x 800, 480 x 854,1280 x 720, 1280 x 800 24 bit PNG or JPEG