Can you help me how to properly setup Google AdWords for my webshop?

So, I have online shop application, and I integrated it with Google AdWords, by adding proper JavaScript into web application.

Problem I have, is that converion Value on Google's Analysis control panel page is 0, despite the thing that I do have Conversions (many-per-click) with value of 12.

Code I integrated looks like this:

Code JavaScript:
var google_conversion_id = <number is here>;
var google_conversion_label = "<label is here>";
var google_conversion_value = <?php echo $charge; ?>;

I added those lines (with several more JS lines required for Google AdWords) into last page on shopping process, when payment has been made on my webshop.

PHP variable $charge have value of sold order.

Despite all of those, my Value is still 0. Can you help me waht I'm doing wrong, and how can I get proper value for it?