To display the item number on the repeater you can use the Container.ItemIndex
property.
<asp:repeater id="rptRepeater" runat="server">
<itemtemplate>
Item <%# Container.ItemIndex + 1 %>| <%# Eval("Column1") %>
</itemtemplate>
<separatortemplate>
<br />
</separatortemplate>
</asp:repeater>