Auto Transaction Numbering - to change last number

User is asking to change a range now for automatic transaction Numbering (Receivables Manager->Setup->Sources->Last Number) - so, may I handle this through the front end - for instance, update that last number for Automatic Transaction Numbering on the Transaction Sources screen? ... or it maybe only done through the backend - to find a sequence for that source_id and bump it up to a needed number?

Another issue  is - I cannot edit the Last Number field on Sources screen - do I need to reset a profile or it is not possible to change from the screen? Tried different responsibilities - it is always shaded, not editable...??