Whitelabs says it's Irish Ale yeast has an attenuation of 69-74% which, if I understand it correctly, means the yeast should convert between 69-74% of the sugars in your wort to alcohol. So if you started with an OG of 1.082 you would do (or how I do it):
82 x (1 - .74) = 21.32
82 x (1 -...