according to the av-comparatives results:
GData - 61% (Avast + BitDefender engine)
BitDefender - 35%
so, can we assume that Avast detected the rest of 26% or am I wrong? 
Actally that's not necessarely true. It was minimum 26%, but it might just as well be 50% or even 61%...
In 2 engine AV's, both can detect the same thing as well so you can't divide that in such a simple way becauuse detection of one can "eat" into the percentage of the other by detecting the same stuff the other product detects.