Secret Doors, Elves, and Casual Inspection

I have some confusion about how Elves casual inspection is supposed to work.

On page 93 of ACKS, the third paragraph has the sentence, “Secret doors can only be spotted if characters are specifically looking for them.” Later in the same paragraph there is a sentence regarding Elves, “Elves have keen eyes that allow them to detect hidden and secret doors with a proficiency throw of 8+ on 1d20 when actively searching, or 14+ on casual inspection.”

I know that active searching involves searching the 10’x10’ area where the secret door is located for 1 turn in order to locate it. What does Casual Inspection entail and how long does it take?

Does it mean that the elf is still taking a turn to search that area, but can be doing other things actively as well?

Does it mean that if they simply walk through that 10’x10’ square they get an automatic chance to spot the secret door without even trying?

Or perhaps it means something else?

Thanks in advance for the clarification.

it means that if they simply walk through that 10'x10' square they get an automatic chance to spot the secret door without even trying.

Thank you so much, Alex.