hexdump Spinebot's answer is correct, so there isn't much more to add. However, I recommend watching the video we published titled "Keying and Easing Techniques: Spine Tips #6" to better understand the advantages of each view and how to use them:

The Curves view in Spine is designed to provide a focused view of the interpolation between two keys, allowing you to adjust the easing and transition more precisely. It is not redundant but rather complements the Graph view by offering a different perspective. The Graph view shows all keys and their values over time, which can be more comprehensive for understanding the entire animation. The Curves view, however, is more specialized for editing the transition between two specific keys.

Regarding the discrepancies you are observing, the Curves view normalizes the time (X-axis) and values (Y-axis), which can sometimes make the curve appear differently than expected. This normalization is why you might see an upward curve when you expect a downward one. The Graph view, on the other hand, shows the actual time and values, which might help clarify these differences. If the values of two consecutive keys are the same, the curve may not be displayed in the Curves view because there is no relative difference to show.