Question: In a 5G-GUTI NAI format, if the <AMF Set Id> has only one significant digit, how will it be represented in the username part of the NAI?
Option 1: The single digit will be appended directly to "set" (e.g., "set4")
Option 2: A single "0" will be inserted at the left side to make it a two-digit coding (e.g., "set04")
Option 3: Two "0"s will be inserted at the left side to fill the required three-digit coding (e.g., "set004")
Option 4: The <AMF Set Id> is always assumed to have three digits, so no adjustment is made.
Explanation: According to the specifications for the NAI format of a 5G-GUTI, if there are less than 3 significant digits in <AMF Set Id>, "0" digit(s) shall be inserted at the left side to fill the 3 digits coding. Therefore, a single-digit <AMF Set Id> would have two "0"s added to make it three digits long, correctly represented as "set004".