The difference between direct and indirect supervisor is the presence of the supervisor. Direct supervision means a supervisor is psychically present.
When mailing a certified letter, a person should expect it to take from three to five days to reach its destination. Depending on how long it takes the recipient to pick up the letter, the process can take up to 21 days. People who send certified mail receive a notification to prove that the letter has been received by its recipient.
Neither can you dispatch international mail as certified mail. Certified mail is likely to travel fairly quickly. Priority mail is guaranteed to arrive at its destination within two to three business days. First-class mail arrival times are also typically within three days or less, according to the Postal Service.