Your team uses Story Points for estimation and tracking.

The two actions that are reflected as scope change are dragging an estimated story from the backlog to the sprint and modifying the estimate value on a committed story. Scope change is a measure of how much work was added or removed from a sprint after it started. It is calculated by comparing the total story points committed at the start of the sprint and the total story points completed at the end of the sprint. If you add or remove issues from a sprint, or change their estimates, you are changing the scope of the sprint. The other actions mentioned in the question do not affect the scope of the sprint, as they do not change the amount of work planned or done in the sprint. References: Viewing the Velocity Chart, Scope change