Many businesses don't want their auctions to start when entered, they choose to schedule them to start (and therefore end) at a later time when they may not be at work any longer. Scheduled auctions start and end on exact quarter hours, so there are spikes in traffic when many auctions end all at the exact same second.
AS monitors internet traffic in real time and will send your bid in earlier if they think there is a chance your bid may not make it in time. This is done auctmatically and there is nothing you need or can do about it.
I would think 7-8 seconds (that's what I use) should work fine.