Gross Sales

• Condition class “B” (price).
• Condition price must have an Account type (Account Key).
• Condition price cannot be a statistical condition.
• Condition must to be active.

In SAP 

Net Sales 

Net Sales = Gross Sales + Discounts & Surcharges + Rebates

Commissions are not considered

Discount & surcharges can be positive/negative in BW

Rebates are always negatives in BW

Take care of the wording : Net Sales in Global Sales <> Net Sales condition in SAP

In SAP