Boss VF-1 Effect Processor

Just got the VF-1, it sounds great (I also have the GT5), mainly 
because I wanted to connect the SPDIF to the comoputer directly, 
however if I make a recording without any input on a reverb program 
for ex (room for ex)i still get about -75db wheras the analog outs 
give me about -80db! Is this a malfunction? you'd expect the SPDIF to 
be more quite and that´s pretty anoying, anyone who can comment on 
that?

Also how do you check the OS version?