Couple of improvements

- better handling of negative numbers
- improved regex pattern
- limits to min and max values

main.js

@@ -651,8 +651,18 @@ String.prototype.format = function () {
 
 function padZeros(val, length) {
     let str = val.toString();
-    return str.length < length ? padZeros("0" + str, length) : str;
-};
+
+    if (str.length < length) {
+        if (str.charAt(0) === '-') {
+            str = "-0" + str.substring(1);
+            str = padZeros(str, length);
+        } else {
+            str = padZeros("0" + str, length);
+        }
+    }
+
+    return str;
+}
 
 function updateActivatedTab() {
     var activeTab = $('#tabs > ul li.active');