Hello; The picture shows the chip well. Sounds like the chip has removed about half of the thickness of the glass at that point and is roughly half way up. As stated in a pervious post, I have 29 gallon tanks in use with smaller and less extensive chips. I chipped them after they were mine. So far no issues.
The price is good for a large tank. I go along with others, in that if the tank can be set up in a basement or room with a floor drain for a few years to see if it holds. I have had a few tanks 55 gallon or larger over the decades. Eventually they all failed and had to be replaced. In my current home, of one year, I removed the carpet from the aquarium room, placed vinyl tile, Siliconed plastic quarter round around the perimeter of the tank area and drilled a drain hole to channel water into the basement. Tanks do fail or get broken quite often. I have only one intact survivor from over five decades.
If you buy the tank; I would consider running a fresh bead of good silicone along the inside seam where rthe chip is and at the same time adhering a panel of glass on the inside of the tank over the area of the chip wide enough to cover the chip and long enough to run from the top to the bottom. Since the chip is on a back corner, I would also consider adhering with silicone a length of angle aluminum (or something similar) on the outside corner where the chip is. (I have seen carbon fiber strips for use as reinforcement. Never tried them, but it might be possible to bond a thin strip of that stuff to the outside.)