Confused about 480p

A competition is requiring video clips to be created as:
"Maximum screen resolution height of 480p with commensurate width to give an overall aspect ratio of 16;9 (w:h)"

I am slightly confused. Either to what does it mean, or/and how to use Premiere (Pro CS4) to generate/export such clips.
Does it mean a video clip of 854 by 480 pixels? I tried to create a Premiere Sequence of that size, but don’t think I was able to.

via Video Editing Forums: Digital Director – Adobe Premiere, Premiere Elements, and After Effects