Hello Karan,
To the best of my knowledge, considering your scenario requirement class that gets determined in R/3 plays a major role here. Usually for main items and sub items the schedule line category is configured differently and the item category as well. So, you would see two different requirement classes getting determined for main item and sub item respectively. The same information is available in the requirements relevant information VBBE (field values BDART PLART concatenated together) in R/3. To consider this as a real time demand, you should consider the relevant sub item based on the requirement class that you see in APO ( check mode in APO ). If I am not wrong, you are trying to upload the key figure "Sales orders" to consume the demand forecast in SNP. Also, if it is about pushing the data to BW for sales history purpose same logic applies.
Hope this helps
Babu Kilari