According to the FoI response below there were 4,045 applications for SO at the original closing date and time but the closing was subsequently extended so the final number of applications will have been higher than 4,045.
DOF/2022-0140 - Response
While the number of applications is checked by HRConnect at times during an
external recruitment competition, hourly numbers are not logged. At the times
of checking, during the Staff Officer recruitment competition, the running total
of applications submitted was 875 by the evening of 6 April 2022, 1,100 by the
evening of 7 April 2022 and 4,045 at 12pm on 8 April 2022.