I've had very tiny pits like that on a car that had a car cover installed outside. Even though the cover fit tight and was tied down in multiple places, small particles of dust and dirt made their way underneath and got rubbed against the paint. It literally sanded tiny pits into certain areas where the cover could move against the paint. I had it tied down to the undercarriage of the car in about 20 different locations, but it still didn't prevent it. The only good thing was in my case it was a project car, so it wasn't that big of a deal. I would never use a car cover outdoors again. It's better to let the car get dirty rather than have the paint get abraded. I would only consider a cover again for indoors, but even then, I'm not sure I would want one. They all will mar to some degree unless you keep them and the paint surgically clean which is tough to do.