Exchange 2013 OWA Public/Private computer setting

Hi

In Exchange 2013 OWA the option to select Private or Public computer is not precent as Default.

Running the following powershell command will enable the checkbox on the logon page.
Set-OwaVirtualDirectory "ex1\owa*" -LogonPagePublicPrivateSelectionEnabled $True

After running that command, the checkbox is there, but how do I get the check box unchecked as default. As it is now the option "Private computer" is the default one, but I would like to have it unchecked as "Public computer" as default.

Is this possible to do? I've googled a lot on the case but not found anything how to change the default setting for the Private/Public OWA.

Best Regards
Lars