Part 451-27 is another detail. Part 451 is under FAA regulations, so if this is a Thai AD, the numbering might be different. The user might be referring to a local Thai AD that follows similar numbering. Alternatively, maybe there's a translation or adaptation of a US AD into Thai regulations.
If this is a CAAT directive:
: Indicates this is "Part 451" of a series with a duration of "27 minutes." ASD Mei 27 Agustus 2023 Bangkok Part 451-27 Min