If your data goes in that column with "\n" (NewLine, usually when you put data for this column from textarea/multiline textbox) then you can use
<asp:TemplateField HeaderText="Amount Desc" ItemStyle-VerticalAlign="Top">
<itemtemplate>
<%# Eval("YourDescriptionColumn").ToString().Replace(Environment.NewLine, "<br/>")%>
</itemtemplate>
</asp:TemplateField>