I'm rather new to Raspberry Pi and have come across a problem I'm sure is common, but which I can't find a solution for. I am attempting to download Rasbian onto a micro SD card for a Pi 3 Model B. When extracting with 7-zip, I receive an error message that there is not enough space on the disk. I have tried this on two 16 GB cards of different makes and models. Both cards are empty, and one is fresh out of the box. I'd like to understand why space is limited and how this can be circumvented.