Order discount if order meets minimum quantities requirement

Use Case:
- Customer places an order for item 'ABC' for different delivery dates.
- Multiple order lines are added for the same item 'ABC' with different delivery dates. For example:
Line 1 with item 'ABC' 100 qty and request date as 10 Jan,
Line 2 with item 'ABC' 150 qty and request date as 10 Feb
Line 3 with item 'ABC' 120 qty and request date 10 March
- Customer should be given 10% discount if order quantity is more than 300.
- Considering total of 3 lines, it meets the criteria for discount. However, system checks quantity at line level and at the order level and hence, discount is not given.