Field help (FFMPCU) 

This field can be modified according to the receipt note transaction setup. Upon using the right button, the system proposes all the units of measure (stock units and packaging units) defined for the product. If this unit is modified, the STK/PAC coefficient is automatically modified, so that the quantity remains identical.

The product can have several packing units:

Only packing type units form the units of measure table can be chosen.