6 - 4 ▁corresponds ▁to ▁an ▁imp lied ▁probability ▁of ▁ ▁( 4 0 %) ▁ 4 - 1 ▁corresponds ▁to ▁an ▁imp lied ▁probability ▁of ▁ ▁( 2 0 %) ▁ ▁By ▁adding ▁these ▁percent ages ▁together ▁a ▁' book ' ▁of ▁ 1 2 0 % ▁is ▁achieved . ▁ ▁The ▁amount ▁by ▁which ▁the ▁actual ▁' book ' ▁exceed s ▁ 1 0 0 % ▁is ▁known ▁as ▁the ▁' over round ', ▁' book maker ▁margin ' ▁ ▁or ▁the ▁' v ig or ish ' ▁or ▁' v ig ': ▁it ▁represents ▁the ▁book maker ' s ▁expected ▁profit . ▁Thus , ▁in ▁an ▁" ide al " ▁situation , ▁if ▁the ▁book maker ▁accepts ▁£ 1 2 0 ▁in ▁bet s ▁at ▁his ▁own ▁quoted ▁odd s ▁in ▁the ▁correct ▁proportion , ▁he ▁will ▁pay ▁out ▁only ▁£ 1 0 0 ▁( including ▁returned ▁st akes ) ▁no ▁matter ▁what ▁the ▁actual ▁outcome ▁of ▁the ▁football ▁match . ▁Ex am ining ▁how ▁he ▁potentially ▁ach ieves ▁this : ▁ ▁A ▁st ake ▁of ▁£ 6 0 . 0 0 ▁@ ▁ 4 - 6 ▁returns ▁£ 1 0 0 . 0 0 ▁( ex actly ) ▁for ▁a ▁home ▁win . ▁A ▁st ake ▁of ▁£ 4 0 . 0 0 ▁@ ▁ 6 - 4 ▁returns ▁£ 1 0 0 . 0 0 ▁( ex actly ) ▁for ▁a ▁drawn ▁match ▁A ▁st ake ▁of ▁£ 2 0 . 0 0 ▁@ ▁ 4 - 1