My memory card shows less space than advertised
If you have received a memory card or USB and the capacity seems to be a little less than you expected, this is normal and probably not due to a fault.
Memory is pre-formatted for immediate use in compatible devices, however if you have formatted it incorrectly or not using in a compatible device this can also give you an incorrect capacity reading.
So if you haven't formatted it, and you are using it in a compatible device and the memory shows less space than advertised, there are two main reasons for this;
Firstly, some of a flash storage device’s listed capacity is used for formatting and other functions and therefore is not available for data storage.
Secondly is the calculation of the bytes and the space used for file management, you can also find an explanation of this on the back of the retail packaging you received.
One megabyte to us mere mortals is equal to 1,000,000 bytes, one gigabyte equating to 1,000,000,000 bytes. Though to a computer with phenomenal calculating power a megabyte is 1,048,576 bytes and a gigabyte is 1,073,741,824 bytes. As you multiple the latter against the calculations of a human, that is where the perceived loss is - in fact 70 MB per GB.
The manufacturer SanDisk has a clear explanation of this on their website, click this link to read the information:
Capacity of the device does not match its label
Read our article of this by clicking on this link: Why Do Memory Cards Have Less Space (MB/GB) Than Advertised?