How about a weight of person plus chair added to the description for more accurate useage of the mat? This was an economical mat for the low pile carpet use but I am not sure if the weight of the chair owner plus the chair will stand up to the mat's life.
Perhaps if they were a few millimeters thicker my wheels wouldn't make dents they may end up cracking the surface. The dents sort of lock the chair in one place and makes it hard to move without some effort.