Why my message box doesn't receive(review) any messages from <list prepend set> object?

Sorry, basic learner here, I wish to review my frequencies going in message boxes as my book showed (Designing Sound), and couldn't figure it out by myself. But does message boxes review any list with only receiving float list?

Because the message expects [set something(, but [list prepend] sends out [list set something(. So you need to use [list trim] after it to get rid of the list selector:

Great help! thanks ingox!