Working with the 0 Column of the Planning Table 
In flexible planning, you can set an initial value or quantity for a key figure at the beginning of the planning horizon, for example, for the key figure "stock level". This value or quantity is displayed in the "0 column", so called because it represents the time prior to the first period in which planning data is maintained.

Key figures in the 0 column are aggregated and disaggregated just like any other key figures.
To display the 0 column:
The 0 column appears at the beginning of the planning horizon. If you have calculated opening stock levels using mass processing, these are now shown here.
This value or quantity will be saved when you save the planning version.
See also:
How to Set Opening Stock Levels with Mass Processing Setting Opening Stock Levels Setting an Opening Stock Level Manually in Standard SOP