Increment in AJAX MultiHandleSliderExtender is not incrementing properly

Question

I am creating an interface which allows the user to select different time ranges from a time line indicating hours from 0 to 24. Therefore i have created a ajax MultiHandleExtender and assign different properties to it as shown below:

<form id="form1" runat="server">
<div>
    <asp:ToolkitScriptManager ID="toolkitScriptManager" runat="server" />

    <asp:TextBox ID="txtSlider" runat="server" /><br /><br />
    <asp:TextBox ID="txtStart" runat="server" Text="50" />
    <asp:TextBox ID="txtEnd" runat="server" Text="140" />       

    <asp:MultiHandleSliderExtender  ID="mhse" runat="server" 
                                    BehaviorID="mhse" TargetControlID="txtSlider" 
                                    HandleAnimationDuration="0.1" Length="576"
                                    Minimum="0" Maximum="1440" Steps="288" Increment="5"
                                    ShowInnerRail="true" EnableInnerRangeDrag="true" 
                                    EnableHandleAnimation="true" RaiseChangeOnlyOnMouseUp="true"
                                    EnableMouseWheel="false" EnableRailClick="false">
        <MultiHandleSliderTargets>
            <asp:MultiHandleSliderTarget ControlID="txtStart" Offset="0" />
            <asp:MultiHandleSliderTarget ControlID="txtEnd" Offset="0" />
        </MultiHandleSliderTargets>                                 
    </asp:MultiHandleSliderExtender>

</div>
</form>

I want to allow user to select more than on range but for the momment i am trying for only one range but even that is not functioning properly I have divide the slider in 288 steps to allow user to make a drag for every five minute not more or less but this gets failed when user selects a range greater than 140 for example when user select a range from 50 to 140 everything is fine but when user exceeds 140 the increment need to be made is 145 instead it is 146 which creates a problem for me because i always want an increment of 5.

I am new to ajax and therfore cannot identify the problem exactly. Any help will be appreciated.

If any one have the information or link of creating a skined MultiHandleExtender will also be a great help.