5 6, creates a projection of rank 1

q)5 6,
,[5 6]
q)type(5 6,)
104h

Then the composition is created:

q)count 5 6,
#,[5 6]

q evaluates expressions left-of-right

• https://code.kx.com/q4m3/4_Operators/#412-left-of-right-evaluation
• https://code.kx.com/q/basics/syntax/#prefix-infix-postfix