c-objc-method-parameter-offset

c-objc-method-parameter-offset is a variable defined in `cc-vars.el'.
Its value is

4

Documentation:
*Offset for selector parameter on a new line (relative to first selector.

[aaaaaaa bbbbbbbbbb:
|<-x->|cccccccc
ddd: eeee
ffff: ggg];

You can customize this variable.