The 'Send' button in the 'More...' menu is for sending models to other devices associated with your MatterHackers account; not for sending to an SD card in the printer. MatterControl used to have a feature that tried to do that, but it didn't really work so it was deprecated a few versions ago.

If you want to print from an SD card, you'll need to use the Export to G-Code function and save to the SD card while it's in the computer.

The item was duplicated because you chose the instance of MatterControl which was connected to the printer, not the printer itself. Essentially, you sent the file right back to the same Queue.