Net vs Gross for LCD?

What do these specifically mean?

Using this LCD standard 19":
Net Dimensions: 16.38"(W) x 16.29"(H) x 8"(D)
Net Weight: 12.5 lbs.
Gross Dimensions: 20"(W) x 17.5"(H) x 5"(D)
Gross Weight: 15.9 lbs.

What is the actual size of the screen, 16.38" x 16.29"? Is this generally summed up as Aspect Ratio = 5:4 (slightly wider that tall)?

And if the Gross weight is 15.9lbs, what is removed to get the Net weight of 12.5lbs?

Thanks!

Is there any way to find out the actual dimensions of the screen? I'm considering this Hanns·G standard 19" at Newegg N82E16824254009.