Defference between number of session and clients in UA

My setup is Webcontainer+Stape+ServreContainer+Universal Analitics
I have some trouble in my mind, why UA number of clients is more than session’s. I think it dependes on Stape request to UA (one session many clients).

Web container UA set and send clientID and sessionId by vars

cid code

function() {
  var customDimensionIndex = 1;
  return function(model) {
    model.set('dimension' + customDimensionIndex, model.get('clientId'));

sid code

function() {
    function s4() {
      return Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
    result = '';
    for(i=0; i<8; i++)
        result += s4();
    return result;

may be it depends on my vars?