My 13" MBP is my first Mac, when using a multi-slot card reader, I notice that not all slots show up as discs. For example, in my PC, each slot is assigned a drive but on the Mac, it only shows one. I want to transfer files from one card to another using the same card reader but can't do it. Is this issue where only one slot shows up normal Mac functionality? Thanks in advance for any insight you kind folks can provide. P.S. I am using a Sandisk Extreme USB 2.0 card reader.