Tuner (plugin) is out of tune

So I’m recording some guitar parts and thought I’d try the steinberg tuner plugin.
It seems to be a tone lower than it should be.
My variax guitar built-in tuner and zoom fx box agree that a low ‘E’ is a low ‘E’ (Ref @440).
However the tuner plugin thinks it’s a ‘D’.
Is it just me?
Signal path = Focusrite OctoPre -> MOTU 828 ADAT port, externally clocked @48k.
Cubase 6.5.0

That “externally clocked 48k”? What happens if you change that to 44.1?

Umm. yes, sample rate mismatch in the project settings.
That said 44.1 so did explain the difference! (and which setting is essentially the master - not the external clock but the project setting).