Question about How can I make duration of the session less than one second?

[Suyu Z. <suy...@ho...>]

Hi all,  How can I make duration of the session less than one second?  
-t secs, --session-timeout=secs	duration of the session in seconds  
for example I tried "pfmon -t 0.5 --cpu-list=2 --system-wide -u -e LAST_LEVEL_CACHE_MISSES"   
it will have "invalid number of seconds for session timeout: 0.5".  
Thanks:)