Water should come out of a RO/DI setup at 0 ppm TDS. Once carbon dioxide and other compounds start entering it, the TDS will rise. That's not important as long as the containers are food-grade and not contaminated.
A TDS above zero out of a RO/DI unit means that the DI is shot:
http://reefkeeping.com/issues/2005-05/rhf/index.htm
That article has more on what happens then.