@azza 

For klaviyo to collect started checkout metric person has to be subscribed.. so if person is subscribed when they go to their checkout page I think this is when klaviyo pulls this info for the started checkout metric

Hi @azza,

Welcome to the Community and hope to provide some insight about abandoned cart emails!

As @Bobi N. mentioned, the started checkout metric is how abandoned cart flows are actually triggered. The Abandoned Cart flow is triggered by the action, "Checkout Started," not by a list. 

Here is an example of conditions set to create abandoned cart conditions:

For more information on flows, here are some helpful docs!
Getting Started With Flows and getting started with creating an Abandoned Cart Flow and a Browse Abandonment Flow.

Hope this helped! Please let us know if you have further questions as well.

Alex