Improve inline comments

Signed-off-by: Jim Zhang <[email protected]>

solidity/contracts/erc20.sol

@@ -22,7 +22,7 @@ import "hardhat/console.sol";
 /// @title A sample implementation of a Zeto based fungible token with anonymity and no encryption
 /// @author Kaleido, Inc.
 /// @dev The proof has the following statements:
-///        - each value in the output commitments must be a positive number in the range 0 ~ (2\*\*40 - 1)
+///        - each value in the output commitments must be a positive number in the range 0 ~ (2^40 - 1)
 ///        - the sum of the input values match the sum of output values
 ///        - the hashes in the input and output match the `hash(value, salt, owner public key)` formula
 ///        - the sender possesses the private BabyJubjub key, whose public key is part of the pre-image of the input commitment hashes

solidity/contracts/zeto_anon_enc_nullifier.sol

@@ -85,8 +85,8 @@ contract Zeto_AnonEncNullifier is
         publicInputs[2] = nullifiers[0];
         publicInputs[3] = nullifiers[1];
         publicInputs[4] = root;
-        publicInputs[5] = (nullifiers[0] == 0) ? 0 : 1; // enable MT proof for the first nullifier
-        publicInputs[6] = (nullifiers[1] == 0) ? 0 : 1; // enable MT proof for the second nullifier
+        publicInputs[5] = (nullifiers[0] == 0) ? 0 : 1; // if the first nullifier is empty, disable its MT proof verification
+        publicInputs[6] = (nullifiers[1] == 0) ? 0 : 1; // if the second nullifier is empty, disable its MT proof verification
         publicInputs[7] = outputs[0];
         publicInputs[8] = outputs[1];
         publicInputs[9] = encryptionNonce;

solidity/contracts/zeto_anon_nullifier.sol

@@ -82,8 +82,8 @@ contract Zeto_AnonNullifier is
         publicInputs[0] = nullifiers[0];
         publicInputs[1] = nullifiers[1];
         publicInputs[2] = root;
-        publicInputs[3] = (nullifiers[0] == 0) ? 0 : 1; // enable MT proof for the first nullifier
-        publicInputs[4] = (nullifiers[1] == 0) ? 0 : 1; // enable MT proof for the second nullifier
+        publicInputs[3] = (nullifiers[0] == 0) ? 0 : 1; // if the first nullifier is empty, disable its MT proof verification
+        publicInputs[4] = (nullifiers[1] == 0) ? 0 : 1; // if the second nullifier is empty, disable its MT proof verification
         publicInputs[5] = outputs[0];
         publicInputs[6] = outputs[1];