Specify register id

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

neps/nep-0488.md

@@ -1061,7 +1061,7 @@ pub fn bls12381_p2_decompress(&mut self,
 #### General comments for all functions
 
 In all functions, the input is fetched from memory, beginning at `value_ptr` and extending to `value_ptr + value_len`. 
-If `value_len` is `u64::MAX`, input will come from the register.
+If `value_len` is `u64::MAX`, input will come from the register with id `value_ptr`.
 
 Execution ends only if there's an incorrect input length, 
 input extends beyond memory bounds, or gas limits are reached.