Official comment
@Ivan - using the "GetNextCounterValue" function you can create as many uniquely-named sequential counters as you like.
Example:
GetNextCounterValue("Ivan")
GetNextCounterValue("ProjectNumber")
GetNextCounterValue("InvoiceNumber")
If you wanted to create a value that is both text and numbers you can do something like:
"Invoice Number:"+GetNextCounterValue("InvoiceNumber")
Note that using the counter function will incrementally increase it by 1 each time.
If you wanted to start at 10000, then you'd need to do something like: 10000+GetNextCounterValue("InvoiceNumber")