You need to remove the period info from the wrong date. Click on the day that has the incorrect info, and where it shows your flow, change that to none by choosing the blank spot above Spotting. Do this for all incorrect dates, and then enter the correct dates. That should correct the ovulation predictions.
When you delete a tracker, you should be prompted to choose whether or not to delete the data. If you check the box, it should erase the data that you've entered, allowing you to start over.
If you have any other questions, please let us know. Hope this helps!