When a customer opens or clicks a notification email or follow-up email from Spently and makes a subsequent purchase from your store within a 7 day attribution window, we attribute that sale to ROI.
Another scenario is when a customer uses a discount code generated by Spently, then we also attribute that to ROI. There is no time limitation for this attribution, as long as the discount code is still valid.
ROI stands for "return on investment". In other words, how much money Spently has helped your store generate.