in the cart object, make sure the Size and text columns are set to unique.
On the calculations tab, create a new calculation as:
totalDiscount:
(Abs([ID] = 829 AND [Quantity] >= 3 AND [Quantity] <= 5) * ([Price] * 0.2)) + (Abs([ID] = 829 AND [Quantity] >= 6 AND [Quantity] <= 9) * ([Price] * 0.25)) + (Abs([ID] = 829 AND [Quantity] >= 10) * ([Price] * 0.3))
the on the discounts tab, create a new discount using the trigger:
Subtotal For Any Column;
If the Subtotal for column "totalDiscount" is ">" "0"
calculation:
Based on column subtotal:
subtotal of column "totalDiscount" "plus" "0"