[Bug] Pricing rule - Discount becomes "0" on Doc save

I’ve put up a pricing rule to only change the margin, The “Pricing or Discount” option is selectable (blank, discount, Price) and I kept it blank (meaning off).

What I expect to achieve is when a Sales Doc is created, for every line item, a certain margin will get applied automatically, while I get to give a discount as I please.

But no matter what I tired, the Discount resorts to “0” when saving the document. I believe this is a bug.

Can anyone verify this in their system??