Steps to Reproduce

1. load attached excel file
2. click "move sheet right" arrow icon to see rightmost sheet

Actual Result

the last sheet is "1234567890-1 (39)"

Expected Result

We can see last sheet "1234567890-1 (41)" as we do in Excel.

Root Cause

When total tab width over a certain limit, tabbox displays tabs in 2 layers. Because sheetbar doesn't have enough height to show 2nd layer tab, some sheets are hidden.
We can see hidden sheets when I enlarge height of sheet bar area (zsssheetbar and z-borderlayout).