Looks like a scratch. Its just a plastic trim anyways. As long as you're sure the stand is completely flat and level, there shouldn't be any pressure to make the tank fail as the silcone/glass is what really holds the tank. The top trim helps to prevent bowing unless its thicker glass like your rimless. The bottom trim is more for asthetics to match the top or lift it a little off the ground in the center.
Is the tank already full? If not, then just take the tank off and see if the plastic can separate at all