I have read Upanishads are 108 , and in the Muktika Canon , Sri Ramchandra enumerates their name to Hanuman when Hanuman asked him the way to salvation.
As far as my knowledge, Upanishads were written mostly between 2000 BC to 700 BC. Whereas Ramchandra lived in 3000 BC as per today's estimate by some hindu scholars themselves.
So how could be possibly cite texts (upanishads) which is yet to come many centuries later ??
I find this chronology highly confusing , if someone can please shed some light on this .