You are not getting sum of orders in grand total because, it is placed as Dimension and not as a measure. If you change the type(or create new measure calculation) of the dimension to measure and place that on Text mark, you would be able to show the total.
Also, I see you have available qty and order qty as other dimensions, I feel that they should also be measure.
If I were you, I would do following
- Convert those dimensions to measure ( Right click on the field and convert to measure)
- Add measure field into filter card, select measure which you want to show on the view
- add measure filed pill in columns
- Add Measure value on text mark.
I hope that works for you.