Field help (TTPRINC) 

Help common to the unit and mass issue processes. 
This flag is significant only when the issue applies to principal assets and their components.
It is activated in order to specify that the entered sales amount must be assigned exclusively to the principal asset; its components are therefore issued with a null value.
When it is activated in mass processing, if principal assets and their components are selected, the sales amount is distributed exclusively to principal assets. The distribution is performed according to the value specified by the chosen distribution key. The FXMCUMCPST - total distribution with components (AAS chapter, MIS group) is used to specify whether the value of components must be taken into account in the value used as distribution key.
The right click option "Dependent parameter" available on this field is used to display the value taken by this parameter.

SEEREFERTTO An example of distribution of the sales amount to principal assets, with respect to the value taken by this parameter, is provided in the documentation of the FXMCUMCPST - total distribution with components parameter.