The total is a pretty meaningless figure as some of the signatures are generic and designed to detect multiple variants of some malware. The same is true of how other AVs count what is detected so there is no way to count and compare apples with oranges.
You can right click the avast icon, select Start avast! Antivirus, Menu, Virus Database, enter an * for the virus name and click search, which currently returns 85,709.