Hey Coby!
If I understand what you need is to increase that number every time you create an object.
For that probably you should use the autonumber attribute that will be increase everytime.
You need to take into account that if you remove an object the autonumber doesn't care and the number will continue increasing. If you want to check that behaviour, my recommendation is to use an integer attribute and create an eventhandler to handle the calculation of the attribute.
Kind regards,
Emilio