I tried some quick searches to actually figure out what this time actually represents, I'm assuming cpu usage? I've noticed it keeps ticking away once I connect... Even if I'm not 'vanished', but If I unload the plugin and load it back it stops.. it will stay at 0. Is this normal behaviour, what is causing it to tick up constantly?

That is the last hook call time I believe. If it keeps going up, performance on the server is suffering.

Yes complaints about performance lately after installing oxide and a few admin plugins. I've seen it as high as 5.09s, now I'm curious how high it would get.. I have been unloading it when I am not online. NoGreen and GroupLimits sit at 0.01s - So is this a plugin problem, or hardware?

Performance of a plugin would all depend on what hooks the plugin uses. "Admin plugins" is pretty vague, so can''t really say based on that. Vanish is generally more resource intensive, especially if you aren't using the "performance mode" with it.

I did enable performance mode. I don't notice problems in game(lag, performance) after 2 hours, it's at (11.69s) and now 6 hours offline it's at (39.07s), no other plugins are doing this, two are at .06 and .01 but they only seem to go up when used, this is why I think Vanish is somehow in constant 'use', I'm curious why..

Are you using the mods more? Sitting in vanish? Adding more mods as time goes on?

I did finally see this link/guide describing the number https://umod.org/guides/server-management/performance

After a server restart, I've never even connected, never used vanish, and it's at .44s already in a day even tho it's never been "used".

  "Vanish" (0.7.7) by nivex (0.44s) - Vanish.cs

Really dont worry about it.