Closing a high-voltage breaker onto a long line or a capacitor bank produces a transient that can reach several times rated voltage. To soften it, some breakers carry an auxiliary contact in series with a resistor which closes a few milliseconds ahead of the main contact and limits the inrush current.
The timing test has to verify two things: the ohmic value of that resistor and the pre-insertion time, that is, how many milliseconds it stays in circuit before the main contact bypasses it. Both drift as the mechanism ages.
Detecting it requires the analyzer to distinguish three states rather than two — open, through the resistor, and closed — within the same record. Sets that cannot do this simply read an early close and report an incorrect time.