On the contour plot at [C1_W1_Lab03_Cost_function_Sol]

I’m clicking through points on one of the lines in the contour plot, but they show different costs for J(w,b). My understanding is that the contour lines represent a cross-section of the 3D cost function at a certain height (i.e., constant cost J(w,b)), so I expect every point on the same contour line to show the same cost value. Am I misinterpreting?