Hi Karen. Thank you for taking a look into this for us and bringing this discrepancy to our attention. We have consulted with our quality assurance department and the FDA recommends the following for vanilla extract sold commercially:

13.35 oz vanilla beans/ 128 oz liquid (1 gallon) = 0.104

0.104 x 6oz = 0.624 oz vanilla beans  

1 vanilla bean weighs around 0.18oz 

0.624/0.18 oz= 3.46

For FDA standards of vanilla extract for sale: 

For 6 oz of liquid, 3 ½ or 0.624 oz vanilla beans are required  

For 4 oz of liquid, 2 1/3rd or 0.416 oz vanilla beans 

Within the liquid of vanilla extract a minimum of 35% must contain alcohol. Dawn is correcting in stating that according to FDA regulation food production of vanilla extract must meet the standard of at least 13.35 oz vanilla beans per every 128 oz of liquid (1 gallon), scaling down to be 0.416 oz vanilla beans per 4 oz of liquid. When preparing in our home kitchens we prefer the amounts listed here, but please feel free to experiment with the amount of vanilla beans used to your desired preference. Happy Baking!