When you add a chart page to a chart with predictions already made for previous chart pages, the new chart pages’ prediction must be trained. That is what is happening now.
If you want to abort this training for the new chart page you may press the Abort Training button at any time. If you do this, the prediction that you aborted training will show up as blank on the chart page. If you want, you can manually train this prediction at a later time by Modifying Predictions and selecting the Retrain button.
Topics of Interest:
What are Neural Networks?
Neural Network – Results Discussion
Troubleshooting Your Model – What to Do if You Feel You Haven’t Been Successful