If you search the catalogue for a single barcode the system brings you to the bibliographic record and then lists all items, not just the one you want.  It is much more efficient to use Item Search, then search by barcode.

Go to the Search option at the top of the screen and click the arrow to the right hand side to create a dropdown menu.

Click the Item search option from the dropdown menu.

This will open the Item search tool.

Scroll down the page to the third overall box where there is a field with Barcode in by default.

Scan or type the barcode of the item into the field beside Barcode and click Search at the top of the screen.

This brings you straight to the barcode you want - very useful where you have multiple items for a popular title.