In response to the first inquiry, AS monitors eBay computer response time on a continuing basis, and when eBay is running slow AS adds to pre-set lead times to ensure that the bid is placed in time for eBay to process and accept it. I have found this to be an invaluable service.
Regarding the two-second addition (nice pic of a python, guy!) I have also noticed this phenomenon. Originally I had pre-set my snipe time at 8 seconds, which I found ideal for avoiding eBay slowdowns while not allowing time for bids reacting to mine. I noticed that the bids were being uniformly entered at 10 seconds. So I changed my pre-set lead time to 6 seconds and now my bids are entered with 8 seconds left, as I had planned, except when eBay is running slow and AS makes an adjustment as described above.