Capacity flash memory products are usually shipped in accordance with 1MB = 1000KB, 1G = 1000MB computing, but the operating system using binary arithmetic 1MB = 1024KB, 1GB = 1024MB,so there are some differences between the display capacity and standard capacity memory products.
Thus, the real capacity is 4GB = approximately 3.6GB-3.8GB 8GB = approximately 7.4GB-7.6GB 16GB = approximately 14GB-15GB 32GB = approximately 28GB-30GB 64GB = approximately 58GB-60GB 128GB = approximately 110-120GB
There is a calculated difference between the manufacturer and your PC, please Google 'Memory card capacity' to get more information.