A block of mass \(m\) is attached to a vertical ideal spring of spring constant \(k\) and oscillates in simple harmonic motion. The vertical coordinate is denoted by \(y\), where \(y = 0\) represents the position where the spring is unstretched, and the upward direction is defined as positive. The system consists of the block, the spring, and Earth. The graph shows the total mechanical energy \(E\), elastic potential energy \(U_s\), gravitational potential energy \(U_g\), and total potential energy \(U_{total} = U_s + U_g\) as functions of \(y\). Which of the following statements correctly relates a feature of the graph to the motion of the block?