1 = PNR starting with '1' are issued from SCR Zone (issued from Secunderabad PRS)
2 & 3 = PNR starting with '2' or '3' are issued from either NR, NCR, NWR, or NER Zone (issued from Delhi PRS)
4 & 5 = PNR starting with '4' or '5' are issued from either SR, SWR, or SCR Zone (issued from Chennai PRS)
6 & 7 = PNR starting with '6' or '7' are issued from either NFR, ECR, ER, ECoR, SER, or SECR Zone (issued from Kolkata PRS)
8 & 9 = PNR starting with '8' or '9' are issued from either CR, WCR, or WR Zone (issued from Mumbai PRS)