I redownloaded the update from this link, 64bit for Windows 8.This time it was in zip format and I ran the DPInst64 file.
It says it is version 15.6.1
I first uninstalled the current driver 15.4.1.1 included the "uninstall driver software" option in dialog box, then ran the setup for the new one. It is still ends up installing 15.4.1.1 instead.
Why?