What are these black marks on my stud?

Brand new 1650w 190mm circular saw. The blade has 18 teeth. I connected this to the underside of a thick slab of ply to make a table saw. I’m splitting a 90x45 down the middle. The gap for my blade is pretty damn wide. What is this black stuff? Ink from the blade? Is the ink meant to come off like that, or? Friction burn? The blade not being appropriate for the thickness of my piece? I’m pretty new at this.