BT BQ 9b(5) :שליש מלגיו או שליש מלבר‏ : is it a third 'from within' [i.e. of the original amount = 33 1/3%] or a third 'from without' [i.e. the combined amount, i.e. 50% of the original]
See the entire entry for mn@lbr adv. from the outside