ActiveRecord Primary Key - Auto increment With Craft Active Record, using the definedAttributes Method how do I set my Primary Key Field to auto increment?

Or does it just calculate another number for the field that has not been used when the record gets saved?

Thanks for your help.
You don't need to define an id attribute in your Craft Records Class - it is created automatically for you on plugin install as an auto-incremented int. You do need to define the id attribute on the equivalent Model though, and AttributeType::Number is fine for that.