what happens when I do this?

my camera has this function that on certain settings when the ISO is set at 100 and its it's a low light situation, it will take six shots and merge them together.( this is to do with reducing noise) Usually it happens really quickly; but if the shutter is set at 0.4 seconds, it will take 6 shots at 0.4 seconds, and try and merge them.
So what happens is something like this.