About createWrapper in effects.core.js

About createWrapper in effects.core.js


Hello,
In this function, we check whether top and left property of the
wrapped elements are Number :
var top = parseInt(el.css('top'), 10); if(isNaN(top)) top = 'auto';
var left = parseInt(el.css('left'), 10); if(isNaN(top)) left = 'auto';
In which case aren't they numbers ?
Thank you for taking time answering this question : )