I had this as a reply that was never submitted ... as you can see, our math (thankfully) agrees! I figured I may as well chime in as I had it written ... now if only I could click that button more appropriately ...
Essentially, this new rule allows you to contribute more rshares to a post / comment than is currently allowed. So, if you want to try to limit your contributions to people who are commenting on your posts, you can choose a lower limit and you'll have the same effect as when you had 100% prior. My guess is probably something around 12.5%.