In the upcoming months, Google Merchant Center will begin tracking more conversion events besides the conversion events attributed to clicks on Shopping free listings, including conversions attributed to clicks on Search web results and other sources. Google Merchant Center has made this change to better report conversion data and optimize the Google shopping experience for your products.
Managing Your Preferences:
If you want Google to stop tracking conversion data in Merchant Center altogether, disable the conversion setting in Merchant Center or Shopify, or unlink your Google Analytics and Merchant Center accounts.
To learn more about conversion tracking, review this article.