You plan to buy items costing 40 units. A fictional offer gives 10 units off a basket of at least 60. Adding 20 units of goods reaches the threshold, leaving a payment of 50. The discount exists, but you spend 10 more than planned.
Compare with the original basket
Write down the intended purchase total before applying the offer. Then calculate the final amount for the expanded basket. The relevant difference is not simply the advertised discount; it is the change from the purchase you otherwise intended.
Keep usefulness separate from arithmetic
The added goods might be useful, unnecessary or a purchase brought forward. That depends on circumstances the calculation cannot decide. Include delivery charges or other applicable conditions when evaluating a real offer.
This example is not a recommendation to accept or reject discounts. It shows why “saved ten” and “spent ten more” can both describe parts of the same decision. Reading a price claim with a clear comparison point makes it easier to see what the offer actually changes.