I hired JG's to grind down some old stumps on my property. I was provided a quote for $300. I was quoted that stumps would be ground down to 10-12 inches below ground level. I agreed to get the work done; but, when I came home on the day, I found all the stumps were only ground down 4 inches below the lawn surface. Also, all the grinding were filled back into the holes - likely in an attempt to hide the fact that they weren't ground down to where they should have been. In the past, whenever I had such work done by other companies, they left the hole exposed; so, I could see that they went down to the agreed upon depth.
I suggest you avoid GJ's and look for a more reputable company.