Purchase Invoice with negative total

ERPNext
1

I have supplier invoice with a total negative value so I assume it should be “is return”… but then I can not add positive items…

item 1 -2 'a 100
item 2 +1 'a 50

If not “is return”:

Incorrect value: Grand Total (Company Currency) must be >= 0.0

if “is return”:

For an item item 2, quantity must be negative number

2

Let me tell you a simple thing, if it is a purchase invoice or a sales invoice, if you want to return it or create a return invoice, the rate should not be negative. Only Qty comes negative.