Well, it's a quarter tone out - same as it is from A#. In theory, anyway.... Have you checked it with a tuner? The math - as I mentioned - suggests it should be 49 cents flat of A# and 51 sharp of A. And my cheap tuner supports that (vaguely), identifying it as a very flat A# - almost off the scale towards A. Of course guitar strings are not perfect harmonic devices.... (google "inharmonicity"...) BTW, it's 2 octaves above that fretted A# (between frets 17 and 18 on the top E string).