VBO help

I am using VBO to set up an Admin view to be able to bulk update CCK Link field (Link module). I set up a component with a condition that content should be type blog entry and in the action I tried to set up updating CCK field in blog content with the value of new parameter that I intend to provide through VBO interface.

When I select a few nodes through VBO and select this operation, it asks me two things.

1) Node identifier 2) value of the URL

What value do I need to provide for Node identifier?