They more the price goes up, the less people will be able to buy, or buy more of the product. So with less people being able to buy it, the supply will gain and/or not decrease as must as it was prior. The reason is, say pencils are coming from the pencil factory, and the price goes up. People can't buy as many as they used too, so the amount of pencils they are selling, decreases. So the number of pencils they have in their supply increases.
Hope this helps.