Field help (PIHTNOTLIN) 

This field indicates the line ex-tax amount: if a quantity has been entered on the line, this field is the result of the multiplication of the net price per unit by the quantity.
This total can be modified to correct, for example, rounding variances. After modification, the unit price is adjusted if a quantity is entered.
A purely financial line without quantity can effectively be entered and in that case only the ex-tax amount of the line can be accessed.