...
On Value Change is a JavaScript expression that is executed any time value of the field is changed. You can use it to reference any input fields, including Field Groups. For Field Groups, the expression is executed when the value of any of the nested field fields is changed. For Repeatable Field groups, the expression is executed when new items are added or removed and when any of the nested fields within any item are changed. In addition to the standard Field Execution Context variables, On Value Change has one more:
...
On Item Change expression is available for Repeatable Field Groups and allows tracking changes of a particular item. model.getIndex() can be used within On Item Change expression to get the index of a changed item.
...
You must delay any updates performed from On Value Change to startingPointData and model using a 0ms $timeout. Because $timeout is not available in Field Execution Context, you must create a utility function in one of the Wizard-level onLoad actions:
...