The activestate manual states

The range (y_min_value..y_max_value) has to include all the values of the data points, or GD::Graph will die with a message.

Which doesn't look like it is true, but it does appear to be causing your issue.
If you change your "Next Code Snippet" to

## Next code snippet goes here
$graph->set(
    y_min_value => 4,
    y_max_value => 10,
    x_min_value => 1,    
    x_max_value => 7
);
[download]

It will work correctly. The only difference being that the y_min_value and the x_min_value are within the range of the data.