docs: explain why 0.95 represents 5% discount

🧠 Logic:
- A 5% discount means the customer pays 95% of the original total.
- Formula: DiscountedTotal = OriginalTotal * (1 - Discount%)
- For 5% discount: DiscountedTotal = OriginalTotal * (1 - 0.05) = OriginalTotal * 0.95
- Multiplying by 0.95 reduces the total by 5%.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan