I thought the number of valid private keys = fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364140 = 115792089237316195423570985008687907852837564279074904382605163141518161494336 (decimal) ?
My bad, thanks for correcting me!
Indeed, the keys are - fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364140. I confused the total private keys with - fffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f - which is p and F
p the finite field of secp256k1.
I updated my post.