Alex,
Did it give that number to 6 significant figures too?
I would take that 15 arcsec with a rather large pinch of salt and it would certainly get you into a religious argument with certain people. I remember an endless discussion with a certain Mr. CJRL on this subject many years ago.
At that level of precision people will also argue about whether you should point the polar axis at the refracted pole or the true pole (they are around 50″ apart at 52N) or somewhere between the two. Even tiny amounts of differential thermal expansion can move the polar axis by many arcsec. I suppose at least Leeds doesn’t have many earthquakes to worry about.