Brake pad shim question

[Gladu]

I changed the pads in all 4 corners. I noticed this extra brake pad shim from the factory that's full of holes. The shim comes with the hardware kit. What is the purpose of it?

https://www.prioritymazdaparts.com/oem-parts/mazda-brake-pads-mount-kit-l2y63329z?c=Zz1icmFrZXMmcz1mcm9udC1icmFrZXMmbD0xNiZuPUFzc2VtYmxpZXMgUGFnZSZhPW1hemRhJm89Y3gtOSZ5PTIwMTYmdD1zaWduYXR1cmUmZT0yLTVsLWw0LWdhcw==