So if u have 8 lakhs limit and you're upgrading from Regalia to DCB. If it's an HDFC agent themself who comes, collects documents and does it for you. They have someway of splitting the limit. So they keep 5 lakh limit for DCB and 3 lakh for Regalia.
I think they only do it offline and this was just that guy thinking he was being helpful - we found out later once the card was issued. Probably because of Diners acceptability issues.