I'm desperate, need help!

Hi,

I’m working in a new project and I’m having trouble with something. My boss gave me this Flash file in full resolution and told me this:

“If you are exporting the flash file as movies to check your animation, don’t do it at full resolution, they will never play back. Instead, do it at 480x270 or 240x135.”

What does he meant with this? I should reduce the BG size in the property panel or there is a more professional way to do it?

Thank you very much in advance!
Lasbi