clarify credit line table

Fixes http://manage.dimagi.com/default.asp?146586#815106

Before:

![screen shot 2014-11-11 at 12 02 17 pm](https://cloud.githubusercontent.com/assets/1757035/4997185/9d7949e2-699a-11e4-9c30-bb1e10d8b630.png)


After:

![screen shot 2014-11-11 at 11 58 50 am](https://cloud.githubusercontent.com/assets/1757035/4997170/74185264-699a-11e4-8756-83c1cb63ed67.png)

@biyeun