Richard,
Thank you for trying out our plugin and reaching out to us. We have been considering adding some additional options to the Purchase event, like including shipping, tax amounts or even use custom values for the purchase event (as we currently allow for the ViewContent and AddToCart events).
Since this is something you are interested in, expect these options to be added to our pro version in the next update scheduled to be released within the week!
Thank you for your feedback and please let us know if there are any other features or options you would like to see.
Regards,
Jacob