Printing Qty - Unit Name ist wrong

If an Inventory Item does not have a Unit Name, printed form shows " Qty " in the Column Header cell for Quantity. If one gives an optional Unit Name for an Inventory Item, this Unit Name will be printed in the Column Header cell instead of Qty. Is this correct or did i miss something in the settings ?
Any comments welcome!

This is what is meant to happen.

If you mix inventory items with different units, then the unit is shown at line level. If all the items use the same unit, then the heading is changed and the unit is shown at line level

Echoing @Joe91, this way your invoices look more specific if you are using a single unit instead of repeating Piece in every single line.

got it, thank you so much