Analysis
NAICS 923 is the 2022 subsector for administration of human resource programs, part of 92 (Public Administration).
It has only one more detailed code, 9231, which covers exactly the same activities; the definition, index entries and statistics are on that page.
County Business Patterns excludes public administration, so there is no establishment count for it.
Official definition
The Administration of Human Resource Programs subsector groups government establishments primarily engaged in the administration of human resource programs.
Source: US Census Bureau, NAICS 2022 Manual.