We base our plans on original and remaining hour estimations. Portfolio does it's capacity-calculations based on the original estimate, not the remaining estimate.
For us, this leads to the following problem:
A story doesn't get finished within a sprint and therefore moves on to the next sprint. the Original estimate was e.g. 10h. During the last sprint 6 hours of work were done, leaving 4 hours of remaining ours (the remaining Estimate value). Portfolio now calculates the full 10 hours of work in the following sprint despite the assignee only will need 4. This is at least not my expected behaviour.