List map problem

Hi all, I am quite new with Dynamo…
I am trying to detect the intersection between a list of objects (symplified as cylinder) and list of floors imported from linked file.
I found a problem when I use the node… in particular it will return and index smaller than the list in input hence it causes problems on the calculation that I am trying to do.Anyone can give me an idea why it behaves like that?



It is the node in Green BTW