Leave it plugged in.
Its needed for every reboot. After server start its not used until the next restart.
Thank you for your answer XPEH, only one more question and I promise that I don't bother you more.
I made the bootable USB, and i plug in and install de DSM, and everything is fine. Now, if I made another bootable USB, can I plug in in my computer without loose information? I wanna say if the computer, during the installation, the computer modifies the pen drive? Or it's the same all the time? If i plug a new USB the computer will still works like now?
If I'm not very understable, please tell me and I make again the question with other words.
Thank you in advance again.