The mistake is in Step #4. The correct interpretation of a line segment bisector is that it passes through points A, C, and B, where C is the midpoint of AB. Therefore, the best correction is:
Step #4 has a mistake. It should say: “Use a straight edge to draw a line that passes through points A, C, and B. This line is a bisector of AB¯¯¯¯¯¯¯¯ .”
This ensures that the bisector is properly represented as the line through points A and B, intersecting the line segment at its midpoint, C.