Why is the increment being ignored?

I'm trying to reproduce this https://www.geogebra.org/classic/qWKKhnvU example on my solution which I made a copy of here: https://www.geogebra.org/cl... so that I can get a better understanding of the capabilities. Everything is working with one exception: if you drag the open point on the ray (With Don't Include Boundary selected), you'll notice that it's not snapping to whole numbers. If you drag the closed point (Include Boundary selected), it snaps to the whole numbers.

The open point is named A and is defined as Point(b) (a point on line b). Line b. Point A has the increment set to 1.

Point B, the closed point, is defined as DynamicCoordinates(A, round(x(A)), 1) which I assume enforcing the increment snap.

Line b is defined as y = 1 with the equation under the Algebra tab defined as y = mx + b. One thing I noticed here which is different from the original example is that line b keeps checking the Fixed Object box on it. When this is checked, you cannot set the increment under the Algebra tab. I've unchecked it, set the increment, and tried to test moving point A, but I noticed that the checkbox is checked again and the increment is not respected/present. I couldn't locate any script or other means of setting the increment on the original example. If anyone could help, I'd really appreciate it. Thanks!