Plastic ABS hardness: what does 2H Stiffness mean?

I'd like to add that 2H is used to test the hardness of plastics. What is the concept of 2H? If you pay attention to it when we study, there will be the words 2H.2B on the pencil. In order to make you know better, I copied some materials. Please have a look to let you know

Mitsubishi hardness test pencil is suitable for testing the hardness of products. It uses the hardness of standard pencils to test the surface of the tested products, and the method to judge the hardness is to see if the tested products have scratches. For example, there is no scratch on the surface of H pencil, no scratch on the surface of 2H pencil and scratch on the surface of 3H pencil, so the coating hardness of the test piece is 2H. Mitsubishi hardness test pencil UNI has 17 models: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H * *, and the pencil hardness grades are 6B, 5B, 4B, 3B, 2B, B, HB, respectively.