[time-nuts] Thunderbolt UTC time offset

[rtime @dslextreme.com]

Hi Everyone;
 I have finally gotten around to getting my Thunderbolt operational.
Everything is working just fine but I do have a question. In the Thunderbolt
monitor screen and the [Time] window I see that the time is 15 seconds off
from my TAC and a little box tells me that the UTC Offset is set to 15
seconds.
 Why would this offset exist and can I somehow reset it to zero?
Best regards, Bob K7HBG

PS,  Many thanks to Whomever it was that posted the "Receiver Sensitivity "
information!