Two symbols of common parameters. Its Format bit is zero, which is what marks this as trigger-based rather than single-user.
A different layout from the SU field of the same name, carrying BSS Color, spatial reuse and bandwidth but none of the per-station parameters — those came from the Trigger. The same field name in two formats meaning two different things is the sort of thing that makes a decoder subtly wrong rather than obviously broken.
HE-SIG-A
Authored in HE TB PPDU . Drawn in 12 frames.