Error while Linking the value from the grid list (more than 1 item) to the Related data in the Parent Interface

From the Grid Layout list i need to add to the other Selected List which is Related Record Data. So when calling this grid interface i am facing issue in the Parent Interface that.

When I am selecting more that one item from the list it throwing me the below error. Please let me know how to rectify it

Interface Definition: Expression evaluation error [evaluation ID = 033a4:c74b3] : An error occurred while executing a save: Expression evaluation error: Cannot update List of DIL Product User Trans; length of assign value list (2) does not match length of the list to update (1)

1. No Error while selecting 1 item from the list

2. If select more that on item from the list it throwing the below error