Video offset in frames?

I might just be missing something simple here, but I’ve just installed a black magic intensity pro for my video output on nuendo.
The only option for video offset is in ms. To me it looks like the sync is out by 4 frames. If I move the audio 4 frames back it is absolutely spot on. But 4 frames is like 1.216 ms … which I can’t put in as a value. Neither 1 or 2 ms offset looks right.
Any suggestions?
what am I missing here?

PAL >>> (1s/25f)*4f=0.16s (160ms)
NTSC >>> (1s/29.97f)*4f=0.1334s (133ms)

Perfect, thanks for that!

Where would you need to input these values? I feel that my video output through the Intensity Pro is lagging, but Im not sure by what value of frames or mili seconds. There is a noticeable difference in sync when I use the default video window within N7.1 and the BMD Intensity Pro.