Hi. I am new to this, so please excuse me asking the most basic of questions. When I flash the HiFi Berry OS to my SD card, does it overwrite the Raspberry Pi OS. In other words, does the HIFi Berry OS contain the Raspberry OS, or do the two OSs exist separately on the SD card. The reason I'm confused about this is that on the "Initial Setup" page it states that "Make sure, you download the correct version for your Raspberry Pi as the system is optimised for each model. If you’re using the wrong image, the Raspberry Pi won’t boot".