Yummie offers several ways to save on your purchase. The 15% Off Your First Order For Sign Up is the headline offer and is best for new customers making their first purchase.
If this is your first time shopping with Yummie, signing up for their newsletter will get you 15% off your entire order. For any subsequent orders, the 20% Off Your Order deal becomes your best bet. This is a sitewide discount, so it applies regardless of what you're buying. If your basket is particularly small, say under CA$50, this 20% off deal will likely save you more than a fixed amount offer might. For example, on a CA$30 basket, 20% off would save you CA$6.
Remember, you can usually only use one offer at a time. It's always a good idea to check your basket at checkout to see which promotion gives you the biggest saving before you finalise your purchase.