Like @DRM , not too sure what you are asking, but perhaps these will help:
How to make this count? Do you mean as a number and not a ratio? If so it’s 12.8
1920 X 1080 (16:9) is 1.7777777
Will export be slower? Not necessarily.
Export time depends on many factors such as number and type of filters applied, length of video, bit rate and so on.