Explanation:
At x=-4, you traverse vertically, and will hit two points that touch the function somewhere.
At y=-1, we have a horizontal line extending from x=-4 to -2, which means that y=-1 applies to x=-4 to x=-2.
At y=-2, we have a horizontal line extending from x=-6 to -4, which means that y=-1 applies to x=-6 to x=-4.
This potentially means that there are two y-values at x=-4. The convention is that a hollow circle (at y=-1) cancels the solution at that point, which means that at x=-4, the only valid value for y is at y=-2.
Therefore the value of y at x=-4 is -2, so (-4,-2) is a solution.