SAP2000 link displacement and joint displacement

My model was concrete and steel composite beam with link as a shear connector. I added force-displacement characteristic in the link properties to defined link performance. After finished running this program, based on table output data, link has already move according to force-displacement characteristic. But if I calculate the displacement move from each joint that was connected by link, there is so much different. this was confusing because link displacement data should be match by joint displacement, I think. Please advice me. Thank you very much