Privacy setting for specific profile type's custom field

Hi

I have set "Appear During Displaying" to "NO", "Searchable" to "YES" and "Privacy options" to YES for a custom field to test what each config exactly does...
I logged in as a user and opened his own profile to verify it. I saw that privacy option for the particular custom field was still set to "shared with everyone", which I presume coming from Privacy control.

I am a bit confused on difference between these three config.

I assumed that selecting "NO" for "Appear During Displaying" works in the same as "only me" for "privacy option". Why this field is still set to "shared with everyone" when "Appear During Displaying" to "NO"? How everyone are able to view it?

Other thing I am curious is that if user selects "only me" for "privacy option" when "Searchable" is set to "YES", this user will be excluded from advance search even if value of this custom field for this user is a match for search criteria?
How about other level of privacy option was selected, like "My friends"?
Only friends are able to view this user on search results if value of this custom field for this user is a match for search criteria?

How these three config work together? any dependency on each other? If not, why they work separately? They all sound like the same purpose to me.

Much appreciate if you can elaborate..
I hope my questions are clear, otherwise I will send screenshots to clarify..

many thanks