You can control how your document numbers are formatted (and if you need to start from a certain number) by using the Document Numbers section of the Settings window. These numbers will then be assigned to sales orders, purchase orders etc. as soon as you save the order for the first time.
To change your document number format:
- Go to Main Menu > Options > Settings.
- Choose the Document Numbers icon on the left.
- Make your changes.
- Click Save & Close.