Form reports display inaccurate data whenever you change the choice fields of your form, but haven’t updated the reports themselves. If you change the options of your choice fields in the form builder (Single choice, Multiple choice, Dropdowns), click on the Update Report link on the bottom page of your report.
You’ll need to update each report you use. Start by updating the default report and continue one by one with your customized reports (if you have any). This will avoid your reports from displaying misleading data after you have deleted and changed some choices in your Form Editor.