By default, if you change the commission rates, it will automatically update the stats/commission for ALL new and past orders on the affiliate dashboard.
However, if you want to make it so that when you update commission rates, it only affects new orders, you can enable this option in the “Debug” tab under the “Saving Data” section:
With this enabled, once the commission has been calculated for an order, it will never be updated again (on the affiliate dashboard), even if you update the commission rates globally, per coupon, or per product.
Please note, the commission displayed for all past orders is calculated the first time the affiliate dashboard is loaded for a coupon.