Zero-crossings: auto setting meaning

Hi Activate friends,

I'm working on a hybrid Activate model that has a lot of discontinuous (activation) events and uses zero crossings.  After changing the the Solver settings for zero crossings (Zero-crossing threshold and Zero-crossing time tolerance) I'm able to get a better performance using a variable-step solver (e.g. LSODA).

Can someone please define what 'auto' means exactly for the zero-crossings?  I haven't been able to find a definition for this yet.  I would like to loosen these values as they seem to be too strict for my model as the Simulation slows in the middle for a long time before starting again with a variable-step solver.  I'd like to know what they are current set to to understand how to vary this. 

Thanks,

Andy