The baseline
The four weeks before you changed it
Taken at the moment you mark it applied and stored, so later edits can’t quietly move what you’re measuring against. Change the date and it re-baselines, which the dialog says while you’re doing it.
What you see
Clicks, impressions and position, before and after
Three cards per page, each showing the last 28 days, the change against the baseline, and what the baseline was. A page changed more than once keeps one card with a timeline on it, and the comparison stays against the first change.
Track a page yourself
For the changes Searchscope didn’t suggest
Marking a finding applied tracks the URL in the finding, which isn’t always the URL you changed. Fixed a cannibalization clash by rewriting the other page? Add that one by hand: the URL, what you changed, and the date.
It fills as you work
Nothing to set up
Nothing appears until you mark something applied or add a page yourself, so an empty tab on a new account is the expected state rather than a fault.