I figured that is what it was, the raw data doesn't match up with the results in the table.
Time is the total running time for 64k writes, write cost is for a single write, so just dividing time by 65536 gives the write cost. This is correct for all listed tests on Linux and Windows except two, the two buffered tests on Linux. I am not sure what went wrong, both write cost values are about 3.75 times to high assuming the total time is correct.