You can have multiple GST Registration Number from single PAN card.
This is allowed in case of multiple business divisions. Suppose you have two business, one a departmental store and another is a restaurant. You can have two separate GSTIN for different business units. GSTIN is a 15 digit number, and the 13th digit is the business unit number, that too in one state, if you have multiple businesses in multiple state, the first two digits will also change. Below is the break-up of GST