The point where you're standing ... (300, 400) ... is 500 m from the origin.
Light takes (500 m) / (3 x 10⁸ m/s) = 1.67 μs to travel from the origin to you.
So when you SEE the clock at the origin read 3.0 μs, you're
seeing it as it was 1.67 μs ago. YOUR clock says 4.67 μs .