Hi nosborne,
Because you are using the "von Mises curve" material model, you entered a table of points to represent the stress-strain curve. (Or you may have accepted the default curve if you picked an existing table. Either way, there is a table of discrete points on the stress-strain curve.)
The calculated strain is larger than the last point in the table ("out of bound"). So the warning message is indicating that it is extrapolating the stress-strain curve based on the last two point in the table ("Use the last segment data").
