1. Create a Sine Wave from meue Tools/Waveform Generator in track 1.
2. Switch Auto Crossfade off and remove the Fade I/O if there is one.
3. Zoom in horizontally to about 30 Samples (change Units of measurement to samples)
4. Mark the loudest sample and activate the object by clicking in the lower half.
5. Menue Object/Trim Objects reduces the object down to one sample.(put a marker on it shift+1)
6. Route the output signal from Track 1  to the input of  Track 2.
7. Arm track 2 for recording and set punch I/O markers approx. 1 secs either side of the sample
8. Check the input level on track 2
9. Punch record.
10.Find the first sample with the marker "1" and adjust the zoom level to allow marking a range to 
   the newly recorded sample.
Now you can measure the offset by marking between the two samples.

The Sienas in my Studio have an offset of 65 Samples.
On my system at home the ARC88 has an offset of 40 samples which is
under 1ms so thats why I never noticed the necessity for this offset
configuration. 
 
In Ver 6.x the boxes to the left and right of 
"Playback while Recording with Record Offset (Samples)"
do not relate to each other.
The left one is "Playback while Recording" (the only way to switch off Background record mode)
The right one is "Record offset"
 
I also checked a Terratec Xfire 1024 sound card and found the offset to be 195 Samples
which is around 4ms - enough to cause timing problems.
The Soundblaster 128  came in at 45 Samples and about 20 Samples wide :)