The key shows the amount it adds, so place it four times — one per amount — for a full set of clock nudges.

Works whether the clock is running or stopped, and does not start or stop it. On a running clock the displayed time shifts by the amount and keeps counting from there.

Rapid presses are combined into one update, so three quick taps of +1 second add three seconds in a single push — and a press immediately corrected by one in the other direction cancels out.

The clock stops at 0:00 and will not go below it. Counting up or down is your board's setting; either way + moves the number on the clock up.