The limit as x approaches 3 from the left is observed based on the upward sloping line. If we observe beginning from x = 2 to x = 2.5 to x = 2.9, drawing closer to 3, we can see that it approaches the point (3, 1), so the limit is the y-value of 1.
The point at (3,1) being hollow does not matter, since we are only asking for the limit as x approaches 3, not the value at x = 3.