Initially, MuniMuni created the goddess with all one thousand arms, but that turned each cluster of limbs into giant blobs. Instead, MuniMuni decided that 42 arms seemed a suitable way to represent the various Buddhist worlds.
Using one hand for normal slaps to the face went fine! Using all the arms on one side caused the deity to topple over, though. So, if you wanted to do multiple slaps, it's necessary to balance that force on the other side. Noted.
All this for science. Yes, for science!