When it was first measured in the 1800's, the height was calculated at exactly 29000 ft. As the surveyors thought everyone would think they had guessed the height, they officially made 29002ft. It is still rising today as the Indian sub continent plate rams its way north into the bottom of the Asian plate and pushes the Himalayas ever upward.
It's not rising that fast. It was revised upwards from 29002 ft to 29028 ft and then to 29035 ft as a result of increased accuracy in the methods of measurement.