SCH-9 looks like the simplest field in the whole segment — just a number — right up until it disagrees with the start and end times sitting a few fields later in SCH-11.
Quick answer
SCH-9 (Appointment Duration) is a plain numeric value representing how long the scheduled appointment is expected to last. It has no meaning on its own; it must be read together with its units, which live in the adjacent duration-units field.
What this field contains
Value
Numeric duration — a whole or decimal number representing the length of the visit, such as 15, 30, or 45
Companion field
Duration units — the immediately following field carries the unit of measure, typically minutes, that gives the number in SCH-9 meaning
Cross-check
Consistency with SCH-11 — a well-formed message keeps SCH-9 consistent with the gap between the start and end date-times encoded in the timing quantity field
Example
Synthetic example Generated by Synthibase
SCH|APT88213^SYNTHIB|FIL55021^SYNTHIB|||||FOLLOWUP^Follow-up Visit^SYNTHIBLOCAL|OFFICE^Office Visit^SYNTHIBLOCAL|30|MIN|^^^20260728090000^20260728093000||||||||||||||SCHEDULED^Scheduled^SYNTHIBLOCAL
SCH-9 is 30 here, paired with MIN in the next field, matching the 09:00 to 09:30 window encoded later in SCH-11.
Where this trips people up
Synthetic data generators that randomize fields independently will happily produce a message where SCH-9 says 15 minutes while SCH-11's start and end date-times are 90 minutes apart. Any downstream system that derives duration from the timing quantity instead of trusting SCH-9 directly will flag or silently overwrite the mismatched value — a class of bug that only surfaces when the two fields are generated in isolation.
Keep duration and timing fields in sync automatically
Synthibase generates SCH-9 and SCH-11 together from a single underlying appointment window, so your synthetic messages never carry the kind of duration mismatch that only gets caught in production.
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