Hansadutta, in 200 Easy she uses various ripening times for the DVI to get to the desired acidity, while Tim Smith is using mother culture; he may just be making the assumption that you know how long to ripen the DVI. Does he give pH targets?
Here's a sheet that I use to calculate mother culture amount for 200 Easy recipes. If the ripening time she recommends is short, I go with 1%, if a half hour, 1-1/2%, if 45 minutes, 2%.
I can't remember which forum member made this list, but I thank him or her for it.