As far as I can see, you are not logging the measurement time yourself and I think it is also not coming from the instrument.
If you measure the system time with tickcount and use each timestamp to report to the table you get a timestamp.
Only thing you need to do is to keep the first timestamp in a shift register and subtract it from all timestamps before stopping the loop, or just after the loop.
The your time series start at zero.
If you need help for this, just ask and I will program a small example.
You are measuring so fast that ms resolution does not work.
I also tried to be sure that the first measured time was zero but I think that opening the file the first time takes a lot of time, relative to measuring.
So do only aggregate measurements in the loop and wait at least 1 ms.
Save the data to a file after the loop and make sure not to have to much data so e.g. stop at 1000 iterations.