If you see this sign as you are working on a problem, then Gradarius is either pointing out a small mistake or checking to see if you are sure of the steps you are entering. It can be seen as something like "it looks like you computed ___ as ___, which is not correct" or “Are you sure this is what you want to do?” or
Additionally, if you see this sign after you submit a solution where you didn’t receive full credit, click on the sign to see some hints about the steps you have missed in your solution.