Did you buy a Memorette micro SD/SDHC card on eBay? Memorette flash memory cards are low end, expensive and slow. They are a discount brand gaining in popularity with consumers who have a low budget. eBay is not the place to buy them, most are fakes. The advertised capacity is not what you will receive. The real problem is there are very few authorized resellers of the Memorette brand on eBay. Buy one from an eBay seller is is unable to advertise they are an authorized reseller and you are almost guaranteed to receive false capacity.
FlashDriveFacts published a very useful and informative article you should read:
It is comprehensive, well documented. If you bought a Memorette card on eBay you need to read it!