Where can I find more info about Cart2Cart discount policy?

You can check Cart2Cart Terms of Services Chapter 2.7.12 for detailed information on a Discount Policy:

Discounts are issued in the form of 'percentage off' and are offered to customers via promotional emails, advertisements, on-site banners or third party communications. You can use one discount code per one order. If you have several coupon codes, choose one with the biggest discount. Discount codes may have validity period or may be issued for a specific product list. Cart2Cart reserves the right to cancel or change any discount without notice, at any time. All discounts are provided for the migration price only and do not apply to any additional options and services. If you have a discount coupon code but didn't apply it at the Confirm Migration step then your data migration price won't include a discount and Cart2Cart won't provide a refund in this case.