Package Tare Small to Medium?

Can anyone plz explain what this Package Tare Small to Medium and Larger packages in Configuration>Shipping/Packaging menu is?
I couldn't get the clear picture of it.

This refers to an average weight applied to the packaging materials used for this size package

kobra:

This refers to an average weight applied to the packaging materials used for this size package

Thank for the reply.
But can you plz explain a bit how it is applied with some figures?

Copied directly from the admin > config > shipping > Package Tare Small to Medium - added percentage:weight

What is the weight of typical packaging of small to medium packages?
Example: 10% + 1lb 10:1
10% + 0lbs 10:0
0% + 5lbs 0:5
0% + 0lbs 0:0

I am also wondering OP's question and it hasn't been answered yet... Maybe I can put it differently...

What is "small" "medium" and "larger"? Are these things defined by weight somewhere? If so, where? How do I customize the definition of "medium" so when my packages go from poly-mailer size to box-size the shipping weight calculation reflects that?

I think I may have worked it out. I posted in another thread already.

http://www.zen-cart.com/forum/showthread.php?p=376883#post376883