Maintenance optimizer questions

I notice Maintenance Optimizer is mandatory for Solution Manager 4.0 as of April 2007, so I thought I'd better try it out now. I am at SPS10. I've gone through the IMG activities to turn on Change Management and Maintenance Optimizer.

I run transaction Solution_manager select a landscape, select tab Change Management > Support Package Stacks. I press button Maintenance Optimizer.

In the resulting page (Plan Maintenance) it asks for fields, amoung others, "message processor" and "Sold-To Party". What are these fields and where is the call down list controlled? The call down list currently includes "Not Selected()", "(0000000001)" and a local manager's name with "(0000000011)". I am uncertain what to set here.