The penetrometer is a device that assists in the assessment of a track's condition.
Penetrometer readings are used as a guideline, and many other factors are considered that may influence the going.
The official track going is declared at the discretion of the Racing Manager.
It is thus possible that the going is declared as "Good", even though the penetrometer reading is (say)14.

0-15 Firm
15-23 Good
23-28 Slightly Soft
28-35 Soft
35+ Heavy