Hello,
As per IFS help info:
This field is used if IFS/Maintenance or IFS/Engineering is installed. The logical code parts available to be connected to the code parts B-J are Cost Center, Project, Object and Not Used. Not Used is selected by default.  Only logical code part Not Used is allowed for code part A. At any given time, each logical code part value other than Not Used can be connected to only one code part. If project administration in IFS/Engineering is used, the logical code part Project must be used in combination with the code part function Project Accounting.  If No is selected for the Code Used field, only Not Used can be selected for the Logical Code Part field.

Project indicates code part used for Project Management (usually together with Project Accounting code part function), Object indicates code part used as object of Maintenance area (work orders etc., usually together with Fixed Assets Accounting function) and Cost Center indicates code part value used in time reporting - here I do not remember where exactly it is used.