This formula's own materials state this directly: confirm final pricing and shipping at checkout — worth understanding why.
This formula's own materials explicitly separate the per-bottle price from shipping cost on the smallest package tier — worth confirming both together at checkout rather than assuming the listed per-bottle price is the complete picture.
Confirm the per-bottle price for your chosen package, whether free shipping applies to your specific tier, and that the total matches what you expect before you submit payment.