How Avast! not detected VBS Trojan downloader in 9 hours after submission?

File name: SR0710459336BR.vbs
Detection ratio: 15 / 56
File type Text
MD5 23f44671b51928a9b5606d9504664db8
SHA1 872287d6b799607c44dae80236764fccfbd9900d
[b]V.T >https://www.virustotal.com/en/file/2418e7fa1300660bf3b5cab23b883c6d55f5f168c2ec29b3a0b8cecd3f81584a/analysis/1465469827/[/b]
Sent via Virus chest.
It is a VBS trojan downloader.