I see this question pop up a lot- that is, the one of “why does the card say it’s ~63mb and not 8GB when I put it in my computer?”. I think it’s easy for us to forget that the simplest of concepts can be impossible to understand until they’re explained. So I’ll just try to fill in that explanation.
The 63mb you see is the Windows-readable “/boot” part of Raspbian. This 63mb is a slice of the total SD card capacity called a “partition.” Partitions almost act like separate drives, and they can be created in a whole variety of different formats, which are just slightly different ways of storing bits and bytes that different operating systems may or may not understand.
Windows uses a few common formats: FAT, FAT32, VFAT, exFAT and NTFS.
Linux understands these, but tends to store its files in one of the EXT formats: ext2, ext3, ext4.
So when Windows comes along and looks at your SD card, what it really sees are two or three separate drives. One of them it can understand, but the others … well it knows a drive is there, but it has no idea how to read it.
So the reason you see only a small sized disk is that the majority of space is used up by a big Linux ext4 partition that Windows has absolutely no idea how to read.
If you fire up Windows “Partition Manager” you can actually see the slices of disk and what they are.
Noooow… here’s where it gets a little more complicated. A disk partition doesn’t have to fill all of the disk, or even any fixed quantity of the disk. And when distributing disk images like Raspbian Jessie it’s sometimes important to be conservative about how big your partition is. Too big, and subtle differences in the size of an SD card might trip you up. 8GB SD cards might be a few bytes bigger or smaller across brands and if you’ve put something important in those bytes ( filesystems aren’t particularly ordered about how they use the space given to them, often intentionally ) then… boom!
So Raspbian Jessie’s main partition is crunched right down to the point where there’s only a few megabytes worth of free space allocated to that partition. When you flash the image to the SD card, this same scheme is copied verbatim and the rest of the SD card is left as empty, unallocated disk. Here be dragons and all that! Linux ( or anything writing to a filesystem ) can use the space that’s allocated, but it hasn’t been given permission to use the empty parts of the disk, even if they are empty!
SO one of the first things we do on Jessie is to “grow” the partition. That is we allocate that empty space to it and say: “Hey, you can use all this space too now!”
And suddenly Jessie goes from having 20mb of space, to having a couple of gigabytes.