The smallest pack is the only one that charges shipping.
$158 plus $9.99 is $167.99 for a 60-day supply, about $2.80 a day. Compare that with $207 for 90 days ($2.30 a day) and $294 for 180 days ($1.63 a day).
Shipping narrows the gap with the 3-bottle pack, which adds a third bottle and free shipping for about $39 more. If you want the lowest commitment, the 2-bottle pack is still the entry point. Confirm the final total at checkout.