Hi web_kings,
Thank you for your purchase.

You will need  to make some changes in code in file :

/wp-content/plugins/wpdatatables/source/class.wpdatachart.php around line 1584

case 'int': 
   $return_data_row[] = (float)$row[$columnKey];  
  break;
case 'float':   
 $return_data_row[] = (float)$row[$columnKey];  
  break;

and replace with this

case 'int':
   if (is_null($row[$columnKey])){ 
       $return_data_row[]=null;   
 }else{    
   $return_data_row[] = (float)$row[$columnKey];  
  }   
 break;
case 'float':  
  if (is_null($row[$columnKey])){  
       $return_data_row[]=null; 
   }else{      
   $return_data_row[] = (float)$row[$columnKey];  
  }    break;                            

With this changes you will get charts like on the screenshot (Selection_016.jpg).

If you want to make charts like on screenshot (Selection_015.jpg) you have to use wpdatachart callbacks and insert that on page where is your chart.

<script type="text/javascript">
jQuery(window).load(function(){    
if( typeof wpDataChartsCallbacks == 'undefined' ){ wpDataChartsCallbacks = {}; }        
wpDataChartsCallbacks[39] = function(obj){                
obj.options.plotOptions.series= {connectNulls: true};            
}
});
</script>

One more thing you have to change in this callback number 39 in (wpDataChartsCallbacks[39]) to id of the chart that you use on page.

This will be overwritten on next update so you have to come back here and do it again.

Best regards.