“Imaginary” is a table that refers to the mathematical term of  “imaginary number.”

What is an imaginary number? according to Wik,

“An imaginary number, in mathematics, is a number in the form bi where b is a real number and i is the square root of minus one, known as the imaginary unit. Imaginary numbers and real numbers may be combined as complex numbers in the form a + bi where a and b are called the “real part” and the “imaginary part” of a + bi. Imaginary numbers can therefore be thought of as complex numbers where the real part is zero. The square of an imaginary number is a negative real number.”

More photos of the table here.