use ERC20 datatype

contracts/p2pix.sol

@@ -215,6 +215,27 @@ contract P2PIX is
             mapLocks[cCounter].expirationBlock >= block.number
         ) revert NotExpired();
 
+        if (merkleProof.length != 0) {
+            merkleVerify(
+                merkleProof,
+                sellerAllowList[k],
+                msg.sender
+            );
+        } else if (_amount > 1e2 ether) {
+            
+            uint256 userCredit = userRecord[
+                _castAddrToKey(msg.sender)
+            ];
+
+            uint256 spendLimit;
+            (spendLimit) = _limiter(userCredit / WAD);
+
+            if (
+                _amount > (spendLimit * WAD) ||
+                _amount > 1e6 ether
+            ) revert AmountNotAllowed();
+        }
+
         DT.Lock memory l = DT.Lock(
             k,
             cCounter,
@@ -228,27 +249,6 @@ contract P2PIX is
             t
         );
 
-        if (merkleProof.length != 0) {
-            merkleVerify(
-                merkleProof,
-                sellerAllowList[k],
-                msg.sender
-            );
-        } else if (l.amount > 1e2 ether) {
-            
-            uint256 userCredit = userRecord[
-                _castAddrToKey(msg.sender)
-            ];
-
-            uint256 spendLimit;
-            (spendLimit) = _limiter(userCredit / WAD);
-
-            if (
-                l.amount > (spendLimit * WAD) ||
-                l.amount > 1e6 ether
-            ) revert AmountNotAllowed();
-        }
-
         _addLock(bal, _amount, cCounter, l, t, k);
 
         lockCounter++;