Multiple RNAi Primary Targets

I just came across this annotation:;class=RNAi

How often does an RNAi experiment have multiple primary targets? It seems to clutter wormbase if one RNAi experiment with multiple primary targets is used to annotate all of the potentially targeted genes as being involved in the given process. In this case, which gene is responsible for the observation? I guess the primary targets are listed in order of likelihood of being targeted?

I wonder how much data from genome-wide studies suffer from this ambiguity?