Within Service Portal, when a catalog item that supports quantities is requested via an order guide, the form does not display the quantity selection box on the form itself as it does normally when accessing the catalog item directly.

1. Log in to a base system (out of box) instance.
2. Ensure that the Service Portal Plugin is activated.
3. In the browser window address bar, add the following suffix to your instance address:
   /com.glideapp.servicecatalog_cat_item_guide_view.do?v=1&sysparm_initial=true&sysparm_guide=25110912372211003e7d40ed9dbe5dd6 
   For example, https://<yourinstancename>.service-now.com/com.glideapp.servicecatalog_cat_item_guide_view.do?v=1&sysparm_initial=true&sysparm_guide=25110912372211003e7d40ed9dbe5dd6
4. In Are you developing for Android or IOS?, select Android.
5. Click Chose Options.
6. Click Checkout.
   Note that each item has the Delete and Edit buttons available on the Checkout page.
7. In the browser window address bar, add the following suffix to your instance address: 
   /sp?id=sc_cat_item_guide&sys_id=25110912372211003e7d40ed9dbe5dd6
   For example, https://<yourinstancename>.service-now.com/sp?id=sc_cat_item_guide&sys_id=25110912372211003e7d40ed9dbe5dd6.
8. Search for Request Developer Project Equipment.
9. Note that there is no option for the user to edit the quantities before submitting the order.

This behaviour is by design in the Service Portal in all current releases. The internal rule base determines the items quantity for the order guide. There is no option to dynamically add new items to the order guide. The items quantity should not be changed after they have been selected already in the rule base.