See the time stamp of f5 logs in a millisecond

As i know, F5 didn't integrate

millisecond timestamp

function to collect millisecond value & append to inbuilt log file.

However you can achieve it via iRule to add extra log function but it will eat extra memory, cpu, process, etc.

    log local0. "[[clock format [clock seconds] -format "%d/%m/%Y:%H:%M:%S.$fract %z"]\]"

You can reach to support team in case concern.