I created a segment based on URL. I only want to create report for those 20 pages. After I put this segment in the workspace, when I add pageview, visits, unique visits and bounce. Everything seems correct ( only show my 20 pages ). But when I add bounce rate, then my list changes to 200+ pages. I am wondering why? Anything special with bounce rate?
If you have just 20 specific pages, what you can do is to pull in those specific values alone rather than the page variable. To do this, in workspace, on the left panel, click the arrow on the page variable to dig into the actual values.
Select the values that you require and place it in the table. this should resolve your issue.
There are some metrics in Adobe Analytics that are visit-based, meaning they persist on every hit throughout the visit. Bounce rate uses these visit-based metrics (specifically entries and/or entry page), so it can sometimes pull in extra data when you have a filter enabled.
Hyder's post is spot-on if you're looking for specific values.