This note by the KECCAK Team refers to Table 1 of "A SAT-based preimage
analysis of reduced KECCAK hash functions" by Pawel Morawiecki and
Marian Srebrny.
"On the Core 2 Duo, the best implementation of Keccak-f[1600] takes
about 1600 cycles for 24 rounds. As an alternate way to present the
time needed to solve the SAT problem, you could express this time
using one evaluation of Keccak-f as unit. E.g., in the first line of
the table. Keccak-f[1600, nr=3] takes about 200 cycles. With 2GHz, a
time unit is therefore 200/(2*10^9)=10^-7 second. So 1 second of CPU
time is about 10^7≈2^23.25 evaluations of Keccak-f[1600, nr=3], which
must be compared to 2^24 in the exhaustive search. The third line is
more interesting: 1852 seconds is about 2^34.11 evaluations, which
must be compared to 2^40."