// start test data
var iniBooks=6;
var curTS=1168448181;// server time
var iniTS=1164943073;// initial time 
var incr=2; // increment 
// end test data

var curBooks=setStartPoint(iniBooks,curTS,iniTS,incr);
setInterval(countdown, 1000);
function countdown() {curBooks +=incr;}

function setStartPoint(iniBooks,curTS,iniTS,incr){
	var diff=Math.round(((curTS-iniTS)/1000)*incr); // difference since inception
	var startBooks=iniBooks+diff;
	return startBooks;
	}