No you're not screwed don't worry. The easiest way to set the CORE exchange rate is to use integers, or at least numbers larger than 1. So if you want 0.01 TIPSHARES/BTS, set BTS to 100 and TIPSHARES to 1.
I can't seem to get the desired results no matter what I enter, but at this point I'm assuming this is a display bug or the CER field has a bug that will not allow me to enter more than 2 decimal places (pretty sure we set 4 digits upon creation which was the default, I could be wrong).
and
Maybe I should word what I'm trying to do this way, if I want to make it
4 BTS / 1 TIPSHARES what do I enter in the CER field?