I created a project in Portfolio, however, when I choose to focus on a specific release by selecting it from the Release drop down, stories which are not in ANY release still show up.
Why do stories not in any release still show up when I choose to focus on a specific release?
Do those stories have estimations applied to them? If so, Portfolio is calculating (suggesting) releases they could be completed in. Those stories will have a light blue background in the Release column in your plan indicating they are calculated values.