If you are comparing your Conversion Rate metrics between Polar and Shopify, you may notice a difference between the two sources. The reason for this difference is because Shopify uses a different formula than Polar uses to calculate conversion rate. These formulas are detailed below for clarity.
"Shopify Conversion Rate" (Polar Metric):
This metric is calculated using the formula Total Orders (from Shopify) / Sessions (from Google Analytics). For example, if you have 280 Total Orders and 8000 sessions from Google Analytics, the Shopify Conversion Rate metric in Polar will read 3.50%.
"Online Store Conversion Rate" (Shopify Metric):
This metric is calculated using the formula Sessions Converted (from Shopify) / Sessions (from Shopify). For example, if you have 250 sessions converted and 8500 Shopify-reported sessions, the Online Store Conversion Rate metric in Shopify will read 2.94%. Keep in mind that the "Sessions Converted" metric can be inferior to Total Orders in the case where multiple orders have been made in the same session. In addition, Shopify has its own method for calculating overall Sessions which differs from Google Analytics, hence why the Sessions you'll see in Shopify will differ from the GA data.
In summary, the two metrics highlight two different formulas for how you can calculate conversion rate, with Shopify's including a generally higher number of total sessions and a generally lower number of sessions converted, hence why the conversion rate metric in Shopify appears smaller. Given the above, most brands will opt to leverage the Polar "Shopify Conversion Rate" computed metric as it shows a more accurate overall look at how many users who visit will result in conversions.