In the Retention dashboard within the "Cohort table - New sales by Month" report, Polar Analytics calculates New Sales by monthly cohort in the following manner:
Polar generates a cohort of customers who placed their first order during the given month.
Polar sums the value of all orders (new and repeat) that these customers placed during the 30 days following their first order.
Example : If a user placed order A on July 31 and order B on August 10, the value of both these orders will be computed in the July cohort new sales.
To compute the same number in the custom reports section using the Total Sales metric:
Select a breakdown by Customer First Purchase Month and filter on the given month
Filter a second time on Days since first order to keep only orders during the 30 days following the first order
Make sure the date range of your custom report includes the entire given month and the 30 days following the end of the given month
The total of this custom report will then match the new sales value you see in the Retention dashboard
