While you're working on customer retention, tracking your Repeat Purchase Rate is key.
The Repeat Purchase Rate measures how many customers come back for at least a second purchase. A rate of 0% means no one comes back, 50% means half of your customers come back, etc.
The whole point of retention is to keep customers ordering. Before that can happen, they have to place their second order and overcome that roadblock.
By monitoring your Repeat Purchase Rate as you work on retention, you can see your work improving your store (or harming it).
This metric moves very slowly so even a 0.01% improvement is something to be happy about. That's why Repeat Customer Insights tracks Repeat Purchase Rate to two decimal places.
Over-time as more customers see your retention changes, that'll increase the rate. That 0.01% improvement today might end up a 1-2% improvement in the long-term which adds up.