Ipek,
So, in my business case I have one production plant, in which I produce Product A as 20 pieces for next Monday. That's my capacity.
????? Production orders do not represent capacity. Production orders (and many other supply elements) consume capacity. In many CTM profiles, 'capacity' is considered to be a constraint, and the CTM engine will only create supply elements that are consistent with the capacity that is available.
But the problem is, these sales orders are not assigned to any customer.
The program you are using is not intended for this purpose. Instead, try APO_BAPI_SLSRVAPS_SAVEMULTI. This program can exercise various BAPI methods. For more info about how to use this program, read the doc contained within the program, or read the docs on the BAPIs themselves.
Best Regards,
DB49