Hi Kathleen! I'm not sure where you're seeing this in Agile Central, So if you have a screenshot I may be able to help more. For your need, though, I would make a custom page with Custom Chart apps. I'd make an app for each Portfolio Item type you want to track, and make a column chart by each type. For instance, making the Custom Chart app settings like this:
Creates a graph like this:
(the x-axis has the project names, but I didn't put them in my screenshot for confidentiality)
If you're not familiar with custom pages and adding apps, check out Extend CA Agile Central With Apps | CA Agile Central Help. I can also give you more info if you'd like. Hopefully that helps!