Answer
Steps to reproduce using the interface
- Open the Broken Y Axis.jmp data table
- Graph—>Graph Builder
- Drop Time on Y-axis
- Drop Time on Y-axis
- Drop Run on X-axis
- Adjust Graph Spacing
- Adjust Y-Axis 250-350 increment 25
- Adjust other Y-Axis 0-6 increment 1
- Modify Legend Color
- Remove graph title
- Click Done

JSL to reproduce using a script
//Broken Y-axis <BR />Names Default To Here(1); <BR />Clear Log(); <BR />dtbroken_1# = Open( "Broken Y.jmp" );
dtbroken_1# << Graph Builder(
Size( 421, 312 ),
Show Control Panel( 0 ),
Level Fill Color( "Medium Light Gray" ),
Graph Spacing( 10 ),
Variables( X( :Run # ), Y( :Name( "Time (s)" ) ), Y( :Name( "Time (s)" ) ) ),
Elements( Position( 1, 1 ), Points( X, Y, Legend( 14 ) ) ),
Elements( Position( 1, 2 ), Points( X, Y, Legend( 13 ) ) ),
SendToReport(
Dispatch( {}, "Run #", ScaleBox, {Max( 102.921195652174 )} ),
Dispatch(
{},
"Time (s)",
ScaleBox,
{Format( "Best", 12 ), Min( 253.201597956072 ), Max( 348.449137149204 ),
Inc( 25 ), Minor Ticks( 0 )}
),
Dispatch(
{},
"Time (s)",
ScaleBox( 2 ),
{Min( 0 ), Max( 6 ), Inc( 1 ), Minor Ticks( 0 )}
),
Dispatch(
{},
"400",
ScaleBox,
{Legend Model( 14, Properties( 0, {Line Color( 16 )} ) ),
Legend Model( 13, Properties( 0, {Line Color( 16 )} ) )}
),
Dispatch( {}, "graph title", TextEditBox, {Set Text( "" )} )
)
);