fix : some ui and

packages/core/lib/utils/first_digit_decimal_formatter.dart

@@ -0,0 +1,24 @@
+import 'package:flutter/services.dart';
+
+class FirstDigitDecimalFormatter extends TextInputFormatter {
+  @override
+  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
+    String digit = newValue.text.replaceAll(RegExp(r'[^0-9]'), "");
+    late String res;
+
+    if (digit.isEmpty) {
+      return newValue.copyWith(text: '');
+    }
+
+    if (digit.length == 1) {
+      res = digit;
+    } else {
+      res = '${digit[0]}.${digit.substring(1)}';
+    }
+
+    return TextEditingValue(
+      text: res,
+      selection: TextSelection.collapsed(offset: res.length),
+    );
+  }
+}

packages/core/lib/utils/utils.dart

@@ -14,3 +14,4 @@ export 'number_utils.dart';
 export 'parser.dart';
 export 'route_utils.dart';
 export 'separator_input_formatter.dart';
+export 'first_digit_decimal_formatter.dart';