RangeValidation going wacko?

I have the following on a Form:
1 <asp:TextBox ID="txtQtyOnOrder" runat="server" Width="40px"></asp:TextBox>
2  <asp:RangeValidator ID="RangeValidator7" runat="server"
3 ControlToValidate="txtQtyOnOrder"
4 ErrorMessage="Quantity on Order must be in the range 0 to 32,767"
5 ...