ASP.Net Range Validator not working for the Specified Integer Range

hi,

i want to validate textbox, so user enter greater than 30

if user enter lessthan 30 than message will display.. for that i use range validator of asp.net

<asp:TextBox ID="txtprice" runat="server" CssClass="textbox" Width="180px"></asp:TextBox>
                                                        <asp:RangeValidator runat="server" Display="None" ID="range1" ValidationGroup="grdsave"
                                                            SetFocusOnError="true" ControlToValidate="txtPrice" MinimumValue="30" MaximumValue="999"
                                                            ErrorMessage="Minimun budget is 30 USA dollor"></asp:RangeValidator>

its give message if i enter less than 30. but if i enter 100 or 200 it also give message

how can i allow that value???