How do you get flagged while pre-moving?

How does this work? By move 40.Kxf2 I was pre moving every move (as SivertGarvik was I suppose) I had 0:08 seconds left and SivertGarvik only had 0:05 yet he somehow flagged me by 0:003 or something in that range, with no checks or invalid moves to stop any of my premoves. Would love someone to explain this to me. 

If what you said about having premoved all of your moves starting with move 42 is true, then it clearly means that the lag from where you live is large enough so that it can't be completely offset by chess.com's lag compensation adjustments.

Your minimum move time was 0.2 seconds, while your opponent did multiple moves costing only 0.1 second.

https://support.chess.com/article/423-why-did-the-clock-times-suddenly-change-the-clocks-seem-broken

All the above, however, only applies to Rapid chess. For other time settings, the minimum and the bank are different sizes: 

RAPID (described above): 500ms per move + 1000ms bank per 2 moves. 
BLITZ: 300ms per move + 400ms bank per 2 moves. 
BULLET: 200ms per move + 100ms bank per 2 moves. 

If you notice that you only experience lag while playing bullet, this may be why. Bullet is much less forgiving of lag. 

/ So I guess this means that the lag from Australia to the US is over the above thresholds.  

Interesting isn't it. You response was well put and I appreciate all the references and even the data.  Thanks for getting back to me!

I don't understand why the minimum and bank values aren't the same for all types of live chess. 

RAPID (described above): 500ms per move + 1000ms bank per 2 moves. 
BLITZ: 300ms per move + 400ms bank per 2 moves. 
BULLET: 200ms per move + 100ms bank per 2 moves. 

Whatever lag you experience doesn't vary depending on the type of game. 

And yet:

In rapid, the bank of 1000 ms is twice the 500 ms minimum.

In blitz, the bank of 400 ms is 4/3 the minimum of 300 ms.

In bullet, the bank of 100 ms is half the minimum of 200 ms.

If your lag is 500 ms per move, you can get full lag compensation in blitz or rapid, but not in bullet.

In bullet, the average of 250 ms lag would be the maximum to be fully compensated.

If lag doesn't vary because of game type, why does lag forgiveness vary by game type?

Interesting video demonstrating lag compensation.  A 30 second game lasts 5 minutes and a 10 second game lasts a minute and a half.

/ I understand that the video is just a demonstration of the effects of lag compensation taken to extremes and that lag compensation evidently works for most people.

I don't play bullet so it really doesn't matter to me personally.  I would like it if someone from chess.com's staff addressed how the current lag compensation structure is the best possible structure.  Have the maximum and bank values every been changed?  

What would happen if they started playing with the maximum and bank values?  What would happen to users from high and low lag countries?  A little math could be tolerated.