💡 How it works: You purchase Sugar as a 50 kg bag. Define sub-products like Sugar 500g, Sugar 1kg, Sugar 5kg — each with their own name, barcode, selling price and GST. When you purchase 1 × 50kg bag, BillPOS automatically adds stock to all sub-products proportionally. Sell any sub-product at the counter — the 50kg bag stock reduces accordingly.