1) The change payment is set in: 
    
 applyPaymentChange: function(paymentchange) {
    if (OB.UTIL.isNullOrUndefined(OB.MobileApp.model.get('terminal'))) {
      return;
    }
    // Set change calculation results
    this.activeModel().set('changePayments', paymentchange.payments);
    
    
 2) this.trigger('updatePending'); is execute in SCO and Tradi mode 
    but doesn't exist a listener in SCO mode 
    
 3)   the listener
    this.receipt.on(
      'updatePending',
      function(ignorePanel) {
        this.updatePending(ignorePanel);
      },
   call to updatePending
  
 4) the function updatePending call to calculateChange
 
 5) In the funtion calculateChange is executed the setter
   applyPaymentChange: function(paymentchange) {
    if (OB.UTIL.isNullOrUndefined(OB.MobileApp.model.get('terminal'))) {
      return;
    }
    // Set change calculation results
    this.activeModel().set('changePayments', paymentchange.payments);
    OB.MobileApp.model.set('changeReceipt', paymentchange.label);
 
Root case:
    The listener is declared in the function receiptChanged, this function only is called in Tradi mode so the trigger do nothing on SCO mode  
    
    
Amount and origAmount are set if changePayment exist
   OB.UTIL.TicketCloseUtils.processChangePayments = function(receipt, callback) {
    var mergeable, addPaymentCallback, prevChange;
 
    // Manage change payments (if there is change)
    if (receipt.get('changePayments') && receipt.get('changePayments').length) {