Tomorrow when they ring, I would ask for a replacement, ok you’ll have to wait but it will put your mind at ease, you have a tank that was dropped and also has a chip in the bottom, that is one big tank to worry about, also consider if you were to ever try and sell the tank for whatever reason, you would have to disclose the information about the chip, which would put almost everyone off buying or buying at a reduced price.
If you are tempted to keep this tank, and remember tomorrow it’s your decision not theirs as it is damaged, I would only keep it if there was a large discount offered.