Fix encoding bits description

Co-authored-by: Ekleog-NEAR <96595974+Ekleog-NEAR@users.noreply.github.com>

neps/nep-0488.md

@@ -399,7 +399,7 @@ Elements from $E(F_p)$ in compressed form are encoded as `[u8; 48]`,
 with big-endian encoded $x \in F_p$. 
 The $y$ coordinate is determined by the formula: $y = \pm \sqrt{x^3 + 4}$.
 
-- The highest bit indicates if the point is encoded in compressed form and should be set to 1.
+- The highest bit indicates that the point is encoded in compressed form and thus must always be set to 1.
 - The second-highest bit marks the point at infinity (if set to 1).
   - For the point at infinity, all bits except the first two should be set to 0; other encodings should be considered as incorrect.
 - To represent the sign of $y$, the third-highest bit in the x encoding is utilized.