AutoCAD 2013 :: Plot / Annotation And Viewport Scale Correlation

Plot scale / Annotation scale / Viewport scale

I couldn’t figure out how these three types of scales are correlated with one another. For example, my drawing unit in AutoCAD is meter. And thus if I need to print my drawing with a scale of 1:200 then I set the annotation scale to be 1:2viewport scale to be 1:2plot scale 100:1000
 
if I need to print my drawing with a scale of 1:20 then I set the annotation scale to be 5:1viewport scale to be 5:1plot scale 100:1000 

I couldn’t derive the rule that controls these three types of scales. This is also quite confusing when working with C3D! Sounds not the same logic is applied.