To benefit from 20% savings, you'll need to be using membership credits.
For example, our 100 download credits package costs $9.95 USD per month and gives you $13 USD of buying power on the site, which means you're effectively getting a 20% savings when using credits.
To purchase using membership credits, you'll need to download the item from the product page, not through the cart. At this time, you're unable to use download credits for cart purchases.
At any point in the month, if you need additional download credits to purchase a new item, you're welcome to upgrade to the next tier to receive more credits. When your subscription renews, it will be at the higher tier. You can also make a one-off credit purchase.
If you've used all your credits for the month, and you prefer to purchase an additional product without using credits, simply add the product to your cart by selecting 'Add to Cart'. Once you have the item in your cart, you'll be able to check out using any payment method you choose.