IDOC number doubt

Hi.

i have a doubt about the Idoc ID that SAP asing automaticaly.

I have a concept that ID is correlative, isnt it?

sometimes i check we05 or we02 an i can see that the sistem, does not use a correlative number for IDocs of same type.

I saw it in Z IDocs particulary.

Is there any configuration that i can do so the system will generate IDocs ID correlative?

Thanks