Filed of View Calculation

Firstly, I am a new member currently in my trial period. I have to say you guys have created a truly excellent solution here. My last couple of days have been full on learning about the software and also the web interface Sincerely, well done!

One thing I wanted to ask about was the FOV in the web interface.
It looks to me - might be wrong - that the sensor size is being calculated from the pixel size and resolution.
I have set up my ASI174MM in TheSkyX (1936 by 1216 pixels) and entered the pixel size in Voyager as 5.86. That should give me a sensor size of 11.345mm by 7.126mm (which matches the specs of the ASI camera).
In the Voyager web interface the sensor size is showing as 11mm * 7mm. When I compare an image to the Voyager FOV it is very slightly off - smaller (so assumed what is shown in the Web Interface for sensor size is not just a round up for presentation purposes, but actually the specific number being used for FOV?).
Is there a way of getting more precise with the sensor size?

Again, thanks for such great software and support materials.