What are these privatek keys here?
This one:
Private key: 0x659756abf6c17ca70e829a43c7752f1417002440be6ddd93e441f8d4b4a85653b20b4cdcc5c74 8207a0daa16191d07a425d8080c276f9412472e0429e61bc355
and this one:
Private key 256bit: 0x376c7486601275fbac571546409b241cfd4093e2def806ba427927139ec9b8df
How you move from 512 bits to 256 bits?
the 256 bit keys is after apply Modulo N (This only can be done once that you already have the extended privatekey complete)
The extended private key (That one of 512 bits) is just a transformation/rotation/multiplication/some other operation of original privatekey, THB I really like that trick, because make people think outside of the box.