Yes, with clarification: Every 5th point of ER changes reproduction by 1%. The break points are at every 0% and 5%. Changing ER by 1-4% does nothing. Therefore if you are engaging in starting point maximization, then you could get lots of points back with no effect by lowering ER to 51% and raising reproduction by 9%. I hear that nobody really does this
I think the math is right, but don't trust it since I haven't had my first cup of coffee yet. But you get the idea.