It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.
After you perform screening at the title/abstract level and the fulltext level, you get the final set of selected studies. The next step is to extract relevant data according to your pre-defined criteria and a data extraction template.
Here are a few recommended readings on data extraction:
"The Systematic Review Toolbox is a community-driven, searchable, web-based catalogue of tools that support various tasks within the systematic review and wider evidence synthesis process. The toolbox aims to help researchers and reviewers find the following: