The optimizer can optimize the crossovers or boxes so that the SPL (sound pressure level) or total load impedance of a given transfer function between two points of the schema matches a predetermined target. The SPL can be optimzied for either each driver output individually or for the combined response.
The target can be made of several different transfer functions (HP/LP, peaking/shelving EQ, Imported transfer function and an overall slope). All of them can be combined.
A nice feature is that one can optimize the response and set a constraint that the electrical load impedance should be kept above a given limit. In the example below the impedance must be above 4ohm, additionally the XO frequency should be close to 3600Hz (note the small box).