Here's my calculations:

According to the book,

METRIC yeast = 75g fresh; IDY equivalent = 25g

HOME yeast = .09 oz, x 28.35 to get grams = 2.55 g

The HOME formula, based on total weight, is .32 of the Metric formula, so 25g x .32 = 8g IDY.

Yep, that's off too.

So let's go with the percentages column instead.

Metric: Flour = 1500 g

Fresh Yeast = 75 g, which is 5% as noted.

Home flour = 17.6 oz = 498g

so 5% of that should be 25g fresh. We need to divide by 3 to get IDY = 8g

.09 oz = 2.5g, this is a ways off the expected 8 grams.

Yup, I think we have another error.

I think that basically, the yeast in IDY form, needs to be 1.6% of the flour weight (5% fresh divided by 3) so 498 x .016 = 7.96g which is .28 oz - let's call it .3 - which is 2.7 tsp according to page 388.

Anyone else what to have a go at the math here and see how close we are?