In balance
The term in balance means the application is examining an equation. One side of the equation must equal the other side for the equation to be in balance. When returning items, the Requisitions application requires that a return line detail be in balance before processing can continue. This means that the quantity ordered (shipped quantity) must be equal to the quantity being kept plus the quantity returned.
Shipped quantity = quantity being kept + returned quantity
The two sides of this equation must be equal for the line to be in balance.