Hey, @Jimi1032 .
The only place your pixel ID should be is in the Facebook Pixel account section in Online store > Preferences. The Additional Scripts field in Settings > Checkout is intended to be used for any customizations that you’d like to have appear on the order status page of the checkout.
Adding your pixel ID in the intended field will automatically track the 6 standard events, including the Purchase event, which occurs when a customer completes a purchase and views the order status page in the checkout. Because the Additional Analytics field is meant for the order status page, this is very likely why you are seeing inaccurate data and why purchases are being counted twice.
Is there a reason why you added the pixel ID in the Additional Scripts field as well?