jpGraph增加了Barplots之间的距离

I have to create a graph with an ancient library called jpgraph, and I can't increase the distance between barplots: ( see attached image )

In case someone wonders, here is the documentation: https://jpgraph.net/download/manuals/classref/index.html

This is the code where i add the barplots:

 // Label align for Y-axis
$graph->yaxis->SetLabelAlign('center','bottom');
// Titles
// @aici
$graph->title->Set('Difference');
$graph->title->SetFont(FF_ARIAL, FS_BOLD, 14);

// Create a bar pot
$bplot = new BarPlot($yAxis);
//$bplot->SetFillColor('orange');
    foreach ($yAxis as $datayvalue) {
    if ($datayvalue < '0') $barcolors[]='yellow';
    elseif ($datayvalue >= '0' ) $barcolors[]='blue';

}

$bplot->SetFillColor($barcolors);
$bplot->SetWidth(0.5);
$bplot->SetYMin(100);
$bplot->value->SetFont(FF_ARIAL, FS_NORMAL, 10.5);
$bplot->SetWeight(0);
//$bplot->numpoints = 1;

$graph->Add($bplot);