Discount not summerized on the invoice template

[bhartidalal]

I am using following merge fields on my custom invoice template, as in the image. 

My invoices shows discount summerized except when the value of discount is in negetive. Not sure what is wrong in my template.  

[bhartidalal · Accepted solution]

I have Grouped based on Charge Model, now my discount is summerized, but one unit added to product quantity where discount is applicable, some please help.