You can manage project numbers under "Settings - All settings - Master data - Projects: Document settings".
Here you can define whether the project number should be allocated automatically, whether the numbering should restart at zero every year, what the start number is, how many figures constitute the minimum length, and what formatting the number contains.
You can use various placeholders for the format. If you hover your mouse over the question mark above the field "Format", you can see which which placeholders are available to you.
If you remove the checkmark next to "Allocate project number automatically", you can allocate the number directly each time a project is created.
If you place a checkmark next to "Restart every year", the menu item "Number ranges" appears in the settings of the master data.
Here you can define the applicable annual start number. It is important that the annual numbering is activated and calibrated before the end of the year, otherwise the changes will not be transferred.