That means it will be completely gone. you should probably wait a few days before you delete it just to be sure it's not a false positive. After say a week, scan it again from the chest and if it still warns of a virus, then delete it.
One more thing, What is the name of the file? Avast puts copies of kernel32.dll, winsock.dll and wsock.dll in the chest under system files. These files are NOT infected, but are there as backup files.
BTW, Welcome to the Forums.