Confused with POP3/SMTP-settings

Okay, logic has never been my strongest skill, so I dare to ask that profane question:

With all my other e-mail clients I’ve been using before, there’s an option in the POP3/SMTP-settings named “delete e-mail from server” where I can choose between the two settings “never” or “if deleted from inbox”. 

With the eM-Client, these settings are named differently. The main setting is called “leave a copy of messages on the server” and I can choose between the two options “remove from server after x days” or “remove from server when deleted from ‘deleted’ folder”. 

This confuses me as it’s just the other way around and also doesn’t exactly match the settings I’m used too. So if I want the mail client to delete e-mails from the server only if deleted from inbox, how do I have to configure eM Client?!? If I unthick the option “leave a copy on the server”, all sub-options are grayed-out. And I don’t want eM Client to remove mails when deleted from the “deleted” folder, but when deleted in the inbox folder! Can’t eM Client stick to conventional naming, like all other e-mail clients (eg. Outlook, Thunderbirg, stock mail-client on my smartphone) do!?! Why does eM client have to play the lone hand there?!? I’ll stop complaining now, but if anybody can help me to choose the right settings, this would be really cool. Thanks in advance.

Basically, for POP3 you can either leave them on the server or delete them as soon as they are downloaded.

You have a few sub-options for leaving them on the server. These settings are the same in eM Client, Outlook and Thunderbird.