So my raspberry pi 3 didn't come with a MicroSD card. That's fine, I had an old Android phone that was just lying around, so I pulled that SD card out of that phone, wiped and formatted it, and tried to load the OS onto this SD card. I used 7Zip to unzip the file onto the card, but it would get 95% complete and it would fail due to lack of space on the card. The card has 8 gb of space and the OS is only 4 gb. What am I doing wrong?