Ecommerce Conversion Rate %

Hi,

We are working through some statistics and looking for a way to make an amend.

Example we have made for example 5703 sales, this is against 144350 visitors, equating to a 3.7% ecommerce conversion rate.

If we based this on unique visitors which was 107368, the conversion rate would be considerably higher.

It makes more sense to display this based on a unique visitors, is there anyway to change this?

Thanks
Justin