The last non-direct click model gives credit to the last click event before a buyer comes directly to your store to make a purchase. It gives 100% of the credit to the last, non-direct touchpoint.
In the example above, that would be Order Legend as the last, non-direct touchpoint. However, if another attributable event came after the Order Legend click, we would not charge:
Direct traffic is often from customers who have already made the decision to purchase because of marketing on a different channel. Last non-direct click attribution filters out direct and organic traffic and focus on the last marketing activity before conversion.
Using last non-direct click attribution, you learn that it was actually Order Legend that drove the final conversion. Direct will be an attributed channel in this model when the customers only trackable event is coming directly to your store (i.e. direct & organic SEO).
To learn more about Shopify marketing attribution models check their blog post.