IPhone 8+ wireless charging possible damage?

So I'll make this short and sweet. Got the new iPhone 8 plus, my buddie gave me a wireless charging holder pad for it. After charging it for a couple of hours, I noticed this strange coloration forming on the charging pad, I'll include pictures, I had the phone on it for several hours. Do you think this caused permanent damage to the phone? I've gotten a new wireless charging device since, but was curious about possible damage?

And here is the UPC code of the product I was using. I think it's like a third party product or something. Anyway just type it in to google and it should pull a picture of it up.

6953666888816

Please let me know your thoughts, I'm stressing

Here are links to pics of the product and damage

Nah