Are you asking how to fix, or what value to use?
The how-to is to use the manage authors dialog and enter the 'right' sort value into the author's sort box.
The right value depends on your use. You, having a kindle and knowing how the kindle munges names, might want to use 'Miller Jr, Walter M' so that the kindle will generate a string that makes sense. Librarians I know tell me to use 'Miller, Walter M (Jr)' so that Miller Sr and Miller Jr will sort together. Using the 'kindle' approach, 'Miller, Michael' will arrive between Miller Jr and Miller Sr.
In the end -- up to you.
