What does the blackboard written by Tom Burleigh, an American master of abstract art, express?

The reason why a work of art is valuable is that it has done something that no predecessors have done, which can be simply understood as expanding the boundaries of art. It is definitely not that he can sell so much money simply by taking a piece of chalk and drawing a few circles on the blackboard, because it illustrates a social phenomenon. For the audience, painting a wooden board black and drawing a circle is completely different from painting a canvas black and drawing a circle. The former is a liar, the latter is a matter of course.