What is the top floor of the King's Building based on this article? What floor is found below that?

Context: The King's Building is a Grade I listed building that forms part of the Strand Campus of King's College London in the United Kingdom. Originally named the College Building, the King's Building was designed by Sir Robert Smirke in the course of the College's foundation in 1829. As the founding building, it was built between 1829 and 1831 on land granted to King's College by the Government to complete the riverside frontage of Somerset House.

There are today a total of eight floors in the King's Building: Basement level, Ground level, Levels 1 to 4, Level 4U and Level 6. The King's Building houses a number of administrative departments, lecture theatres, the College Chapel, the Great Hall, various function rooms, study rooms and a catering outlet.

Answer: The top floor is Level 6, and below that is level 4U.