Diagnosis
On the item overview, you have selected a number of items in order todisplay the details screens for these items.
You are now looking at the detail screen of one of the selected itemsand want to get data from the previous item using function Item-.
As the data you are looking at is from the first selected itemwithin the item overview, this message appears.

Procedure
Choose function Item + to move in the other direction or go backto the item overview screen using function key F3 and reselect asrequired.