Well the latter .392 isn’t really a program update as such, program versions are normally the 9.0.2018, so that is the version and build number normally seen in the program version. The suffix .391 or 392 isn’t even reported in avastUI > Settings > Update.
Some time ago, I believe something was posted in the forums about the full numbering (including the .391) was something to do with virus definitions or the avast setup/installation file. I can’t recall exactly, but it wasn’t considered crucial/important.
If you download the avast setup file from avast (http://files.avast.com/iavs9x/avast_free_antivirus_setup.exe) that shows 9.0.2018.392.
