Chunk missing from tires, please help!

[JPrieur]

I recently bought a set of Michelin PS2 Runflats off Ebay. The set had '50 miles' on them but one of the rears has a chunk missing from the tread. I have already contacted the seller and I am waiting for a reply. The object in the picture is a penny for scale purposes, and the depth of the 'pit' is about .4 of an inch.

I just want to know if this compromises the tire at all?

Thanks in advance.

[GH41]

I am no expert but it looks like another defect to the left of the missing chunk. GH