They used the same config as TCEC.
"Stockfish was configured according to its 2016 TCEC world championship superfinal settings: 44 threads on 44 cores (two 2.2GHz Intel Xeon Broadwell CPUs with 22 cores), a hash size of 32GB, syzygy endgame tablebases, at 3 hour time controls with 15 additional seconds per move"