...
If the Show Allocation Results only for the Selected Row check box is not selected, the table in the lower pane contains the results of each cost allocation of all costs to the projects (the amounts can be edited). If this check box is selected, the lower table contains the results of allocation only for the cost which is selected in the upper pane's table.
If you need to adjust the allocation results, it is recommended that you do it for each cost separately. For this, select the Show Allocation Results only for the Selected Row check box. You can select the cost in the upper table and review the allocated amounts in the how this cost amount is allocated in the lower table (see the screenshot below).
...
Also, if you want to allocate only a partial amount of the selected source cost to projects, you can add a row and for the <Not Related to Projects> value in the Project column specify the appropriate factor.
...