The repeat % is one of the most important metrics brands focus on, and is closely related to churn rate.
In our Customer Cohort module on the Customer Analytics page, we report the number of first-time customers ("Customers") from each monthly cohort. When those first-time customers make additional purchases ("repeat purchases") over the following 30/60/90 days (labeled M1, M2, etc.), we report those customers who made repeat purchases as "Repeat Customers". Finally, we calculate the "Repeat %" as simply:
Repeat % = Repeat Customers / Customers
Note: This is different from what "Returning Customers" is in your Shopify Analytics report.
Shopify is reporting the total number of repeat customers who made additional orders in a given time period, which is different from the cohorted view above.
I hope that answers your question. As always, reach out to team@tresl.co if you have other questions, thanks for reading!