Use this parameter to remove the Full Access permissions to the mailbox specified by the Identity parameter from the user ...

Use this parameter to remove the Full Access  permissions to the mailbox specified by the Identity parameter from the user specified by the TrustedUser parameter. This parameter accepts the arguments True or False. These arguments are not case sensitive. When using a CSV file, specify RemoveFullAccess True to remove the permission or RemoveFullAccess False to not remove the permission. Specifying False will not add the permission if it is already set. To add the permission, use Add-MSOnlineMailPermission.