Let me tell you the reasoning about this. When we submit any message to SMSC, they issue us a unique message I’d against each message. It can in decimal or in hex. Subsequently when they provide us DLR they should use exactly the same message ID in DLR so that our system can match both and update records. But we have seen few SMSC do not following this pattern.
During submission they issue message I’d in Decimal , but in DLR they change it to Hexadecimal. Though the conversion value of both remains same but our system can’t recognize this. This is the reason, we have provided this feature. You can cross check with your SMSC, if they behave as per expectation, then keep it Decimal, but if otherwise, we have this option to rescue you.