Hello captain

, just as I edit some videos with the trial version editor (Camtasia) and googled Sony Vegas I found something weird.
Based from my knowledge, 1 second equals to 1000 milliseconds.
Until I realize something weird in the following picture for example.
(found on google)
Notice in the timeline. Second is switched every "0;30" thingy.
So my question is what does the "numerical value" smaller than seconds represent?

It can't be in milliseconds, otherwise it will need "0;99" instead of "0;30"