Help identifying mystery foam piece

While upgrading my hinges, a mystery foam piece came out of my laptop from around the left hinge area.

Can anyone help me identify what this piece is and where it should go?

Edit: I have a bonus question as well. The new hinges came with these two tiny screws.

What are they used for? Does the 4.0 kg kit screw in differently than the 3.3 kg one?