I now see what’s wrong:
You’re counting months with your custom query function backwards:
<?php echo date("M",strtotime("-1 Months")) ?>
<?php echo date("M",strtotime("-0 Months")) ?>
and get this result (from source viewer in js function):
function drawChart() {
var data = google.visualization.arrayToDataTable([
['Month', 'Total'],
['Jul', 0],
['Aug', 0],
['Oct', 0],
['Oct', 0],
['Dec', 0],
['Dec', 0],
['Jan', 0],
['Mar', 0],
['Mar', 0],
['May', 0],
['May', 0],
['Jul', 50.34],
['Jul', 50.34]
]);