Hamelman yeast percentage

Hello,

 I have been using Jeffrey Hamelman's "Bread" for a few months now, but only now I found something that I dont understand.
I am a little bit confused about the percentages of instant dry yeast. Lets take the first recipe in the book, the baguettes with poolish, for example. He says you have to use 1.1 percent of yeast in total. I am using instant dry yeast, whereabout he says that you have to multiply the amount of yeast by .33.