Agreed, it's not very clear.
The 11-1115 has a 30/40 spring rate (in pounds per inch, or lb/in).
The 11-1109 has a 35/45 spring rate, so it's a little heavier/stiffer.
It sounds like they have the same physical dimensions, so they can work for the 400 or the 440.
I looked at the Progressive Suspension web site and they don't list any fork springs at all - just shocks.
The installation manual PDF on Dennis Kirk for the 11-1109 seems to be for Goldwings: it references GL1000, GL1200, and GL1500. It also references a chart that is not actually part of the document.
I think you would be fine with either set of springs and making adjustments in the fork oil type.