What’s happening is that you may have crashed or otherwise dumped the drive without properly ejecting it. It leaves a folder in the /volumes directory with the original name of your drive so your Mac has to modify the original name because of the conflict when it mounts.
To fix, go to the Finder, Go menu, Go To Folder option, type “/volumes” and return. You’ll see the directory of shortcuts/aliases to the drive(s) you have mounted and a folder by the original drive name.
Eject the “[original drive name] 1″ alias version (which is mapped to the drive until ejected) which will dismount that alias, then delete the [original drive name] folder. Remount the drive (by unplugging it and plugging it back in or whatever) and the drive will now mount properly and take on the proper alias (sans ” 1″).