Retrieving an Element from list

Well I have another problem.
Hi again.. the queion I have about this GH deffinition is the next: why is not working the "retrieve Item Index"?, I expected to have a result the next result: 0/0/0/1/1, but instead I have all "-1". Does anybody know what happens with it?. Probably I'm not useg it correctly. THanks a lot.