record latency adjustment??

I must have gone into nerd mode
dont know why but i decided to check out the accuracy of this field
 
I had a bass drum playing single hits 4/4
 
set up a mic
un-checked the asio reported latency
and recorded the bass drum
 
I then muted the recording just made
checked the asio reported latency box
 
started the bass drum again(mic in the same position)
 
and recorded a second take
 
Now according to the driver settings in Soanr my  input latency is 150 samples and output is 228 samples = 378 samples
I expected that in the 2nd recording that the transients would have moved to the left 378 samples
but they had only moved approx 250 samples to the left
 
I know we are talking about insignificant differences here, but does anyone
know why there is a discrepancy??