Odessey and Oracle

According to the Zombie Heaven liner notes, fifty years ago to-day (1 January 1968), the Zombies did some work on Odessey and Oracle.  The entry reads "EMI Abbey Road Room 53 Odessey & Oracle original master (stereo)."  As with the corresponding entry for 28 December, I'm not entirely sure what this means, but I'm assuming it indicates when the Zombies gather together the stereo mixes for Odessey and Oracle.