[Solved]-Highcharts returning error 14-Highcharts

Highcharts Error #14 clearly says

String value sent to series.data, expected Number his happens if you pass in a string as a data point

data point is the yValue, if your serie.data is of the form

[y1,y2,y2] 

or

[[x1,y1],[x2,y2],[x3,y3]]

or

[
{ x : x1 ,y : y1 },
{ x : x2 ,y : y2 },
{ x : x3 ,y : y3 }
]

In any of the above forms the type of data stored in y1,y2 & y3 should be numeric. You can achieve this my simply using the parseFloat() or parseInt() in javascript

var serie1 = usage_data.map( function(e) {
            return [e.gateway, parseFloat(e.val)];
});

or do it in the server technology that you are using
In (PHP 4 >= 4.2.0, PHP 5) floatval() can be used

$float_value_of_var = floatval("123.456");