Setting Label Text To Number Of Rows With JQuery?

This is my code but nothing happens.

$(document).ready(function() {
var totalRows = $("#<%=GridView3.ClientID %> tr").length;
document.getElementById('Label6').InnerHTML = totalRows;
});

this is what i ended up using

var rqnum = $("#<%=GridView3.ClientID %> tr").length - 1;
document.getElementById('rqnum').innerHTML = rqnum;
var oknum = $("#<%=GridView4.ClientID %> tr").length - 1;
document.getElementById('oknum').innerHTML = oknum;
var xlnum = $("#<%=GridView5.ClientID %> tr").length - 1;
document.getElementById('xlnum').innerHTML = xlnum;
var dynum = $("#<%=datalist1.ClientID %> tr").length / 3;
document.getElementById('dynum').innerHTML = dynum;

this way it subtracts the header, however, how can i make it so if it is 0 dont subtract the -1 because i dont want negatives