CORNANT informs correlator operations of the number of stations scheduled. This helps determine when all logs and media are in and helps determine what the correlator load, both in terms of drives needed and output data rate, will be. See the discussion of CORCHAN for a formula to calculate the output data rate.
The default value for CORNANT is the number of antennas scheduled which will nearly always be correct. There should be no need to specify a number other than in some special, very strange cases such as when more antennas are scheduled than will be correlated.