An incorrect badge count on the WhatsApp icon is usually caused by an issue with your phone. Try these troubleshooting steps to reset it:

• Ask someone to send you a new WhatsApp message: This should automatically refresh the message count.
• Ensure badges are enabled in iPhone Settings: Go to iPhone Settings, tap WhatsApp > Notifications, turn Badges on or off.
• Reset notification settings: Go to WhatsApp Settings, tap Notifications > Reset Notification Settings.
• Uninstall WhatsApp: Touch and hold the app, then tap Remove App > Delete App > Delete. Then re-install WhatsApp.