You can see how an expression is read this way:

    (defun how-is-it-read? (string)
      (write-to-string (read-from-string string)
                       :pretty nil))
    ==> HOW-IS-IT-READ?

    (how-is-it-read? "#'foo")
    ==> "(FUNCTION FOO)"

    (how-is-it-read? "(remove-if-not #'evenp '(1 2 3 4 5 6 7 8 9 10))")
    ==> "(REMOVE-IF-NOT (FUNCTION EVENP) (QUOTE (1 2 3 4 5 6 7 8 9 10)))"

You can see that this does not match your expectation. Are you actually trying to type that code and evaluate it at a Lisp listener? If not, you should.

Now, FUNCTION is a special operator that in this case returns the function named EVENP.

QUOTE is a special operator that just returns the object it is passed.

So REMOVE-IF-NOT will get called with two arguments: the function named EVENP, and a list of integers from 1 to 10.