batter-like

Hi. I've set a dough of Peter Reinharts Struan from WGB, made with whole grain rice. However the soaker became more batter-like or porrige-like than what I expected, which resultet in a very very wet final dough. Because of this I added a lot of extra flour  to get the kind of dough that I'm used to. I can't find another explaination than that I've misread the instructions or measured wrong (I suspect my weight to not be entirely good). Have other had similar experiences?