This help page explains the settings for our Discount feature:
If you'd need your discount to apply across a range of different products, you'd have to set up a series of discounts for All Cart Items that take a flat amount off the order total when minimum quantity thresholds are met -- e.g., when Min. Item Qty.=2, it would take a flat $5.95 off the order total, Min. Item Qty.=3 would take $11.90 off, etc.
If this discount applies only to various quantities of the same product, you'd set up a series of product-specific discounts that alter the per-unit base price of the item when min. qty. thresholds are met -- e.g., when Min. Item Qty.=2, it would take $2.98 off the price of each unit (since $15.95 / 2 = $7.97 each, rounded down), Min. Item Qty.=3 would take $3.97 off each unit, etc.
Another way of approaching this for varying quantities of the same product is explained here: