Note that RIP is designed so that a routing entry is replaced only if information is received about a shorter route; ties go to the incumbent, if you will. This means that once Router RD creates an entry for Network N1 with a cost of 3 going through Router RB, if it receives information that it can reach Network N1 at the same cost of 3 through Router RC, it will ignore it. Similarly, if it gets Router RC’s information first, it will ignore the information from Router RB.
This seems to be a variation on the baseball-related expression tie goes to the runner. But even after having looked it up, I'm still not one hundred percent sure if I understand what the author is trying to say there. Could you please dissect it for me bit by bit?