diff -r 84a69203c945 web/org.openbravo.retail.posterminal/js/model/order.js
--- a/web/org.openbravo.retail.posterminal/js/model/order.js	Tue Nov 05 12:55:45 2013 +0100
+++ b/web/org.openbravo.retail.posterminal/js/model/order.js	Thu Nov 07 13:19:41 2013 +0100
@@ -767,7 +767,12 @@
             this.createLine(p, qty, options);
           }
         } else {
-          this.createLine(p, qty, options);
+          //remove line even it is a grouped line
+          if (options && options.line && qty === -1){
+            this.addUnit(options.line, qty);
+          } else {
+            this.createLine(p, qty, options);
+          }
         }
       }
       this.save();
diff -r 84a69203c945 web/org.openbravo.retail.posterminal/js/pointofsale/view/keyboardorder.js
--- a/web/org.openbravo.retail.posterminal/js/pointofsale/view/keyboardorder.js	Tue Nov 05 12:55:45 2013 +0100
+++ b/web/org.openbravo.retail.posterminal/js/pointofsale/view/keyboardorder.js	Thu Nov 07 13:19:41 2013 +0100
@@ -96,7 +96,7 @@
           return true;
         }
         if (keyboard.line) {
-          if (keyboard.line.get('product').get('groupProduct') === false) {
+          if ((_.isNaN(value) || value > 0) && keyboard.line.get('product').get('groupProduct') === false) {
             me.doShowPopup({
               popup: 'modalProductCannotBeGroup'
             });
@@ -104,7 +104,10 @@
           }
           me.doAddProduct({
             product: keyboard.line.get('product'),
-            qty: value
+            qty: value,
+            options: {
+              line: keyboard.line
+            }
           });
           keyboard.receipt.trigger('scan');
         }