The Data Difference Warning screen will appear when one of your data sets has changed. This may occur if you manually update your data, or if data which is automatically refreshed (e.g. from a URL, R code, or an SQL database) changes.
The screen tells you about variables that have disappeared, changed, or which are new. It will also tell you about dependent variables (e.g. calculated JavaScript variables) that have been affected by the variables that have changed.
The screen will re-appear until you click Accept.