He condensed the work down to 493 words, no less.
Do you think "no less" is a comment on the number of words? I did originally, but for that to make sense it must be "no more."
Instead, it seems that "no less" is used as an expression to mean "can you believe it?" or something similar.
If I wrote "You must write an essay of 500 words, no less" you would (hopefully) understand that I mean that you must have 500 words as a minimum.
This literal meaning is what my mind goes to when reading this sentence. Since it was meant as an expression of wonder and not a literal limitation on the number that precedes it, I find it a poor expression to choose.