well, let's take a peek, "m" is drawn on the x-axis most likely and H(m) is drawn on the y-axis, making a straight line.
so at m = -5, namely 5 minutes before he was told to go home, the kite was 375 meters up.
then he was told to go home, when m = 0, and the kite was 300 meters up.
now, as far as the other numbers, m = 5, 5 minutes after he was told, the kite was 225 m up, then 10 minutes later, then 15 minutes later then 20 minutes later m = 20, the kite was at 0, namely on the ground, he already had rolled up all the kite string that he was coiling up, so he can pack it in his carriage bag and go home.
