HI takkularapsis,
The plugin allows you to programmatically control the default value of a text input field in Contact Form 7, via a shortcode.
If you have a shortcode that produces the unique reference number you want, you could add that into the form, either as a text or hidden field. (You can use any shortcode that returns a text value, or write your own custom shortcode to generate the value you need – there is no built in shortcode for unique reference number generation).
You could then include that value in the email that gets sent to you via mail tags, just like any Contact Form 7 field.
That said, if you want to generate a number *after* form submission, this plugin won’t help you, as these values are generated when the form is generated (on page load), not on form submission.
Hope that helps