The Google Search Console is introducing a new score called CLS, which stands for Cumulative Layout Shift.
This measures how much of a webpage's layout shifts after the initial loading of the page. This applies to thing like third-party app features that might not load until after the initial page load. This also ties into the lazy-loading present in your theme. Lazy-loading means that not all images in a particular page are loaded at once, some images load in the background after the initial page load. This is to speed up the loading of each page.
So the CLS score could be impacted by lazy-loading as well as app's that load their content/feature after the initial page load.
This is a new ranking from Google, it's not actually being factored into your ranking. You are seeing a sort of preview of a new measurement that will begin to contribute to your site ranking in 2021.
Google has a little more information about this here.
For the rest of 2020 at least, this is not something you will need to worry about. Google is giving a sort of "sneak peek" as to what is coming next year, but as of this moment and the rest of 2020, this score does not affect your ranking in Google.