See a number space wrap around

An integer label can be small while its serial is newer.

• Domain Name System (DNS) zones are named portions of DNS data. Their Start of Authority (SOA) record includes a serial identifying a version of that zone. A primary supplies zone data and secondary servers keep copies. RFC 1982 defines the arithmetic used to compare those serials; it updates RFC 1034 and RFC 1035 rather than replacing the DNS protocol (§§1,7,8).
• SERIAL_BITS fixes the width. Integer labels run from zero through 2^SERIAL_BITS−1, but as serial numbers no label is an absolute minimum or maximum: every serial has a successor and predecessor. Zero is an ordinary serial value, not an uninitialized marker (§2).
• The RFC’s smallest meaningful example uses two bits and labels 0,1,2,3. Adding one goes 0→1→2→3→0. In this space 0 is greater than 3 under serial comparison even though ordinary integer comparison gives 0<3 (§5.1). The clockwise direction is a drawing convention for increasing serials.
• RFC 1982 states definitions, undefined operations and operational cautions; it predates RFC 2119 terminology. This guide does not invent uppercase MUST/SHOULD/MAY requirements. A chronological version history, date-format convention or trust decision is not encoded by an integer label alone (§§2–3,9).