Problem trying to pass the position data from one hierarchy to another Hierarchy via XPresso

I thought I understand how the Hierarchy node works but I was wrong.
I have Joints parented in one null and Text in another null. Then trying to pass the Joints’ position to the Text splines’ position by matching the index numbers via Hierarchy nodes. So the texts and joints are in the same position based on their index in their Hierarchy. Each Hierarchy strand, Joint and Text, works great. I can change the color or position by remapping their index with the Range Mapper node. But I get an error as soon as I plug the Global Position from Joint Hierarchy to Text Hierarchy. Anybody know why?
Thanks in advance!