2,200 households watched yesterday's Twins/Astros game, according to Nielsen (and via David Barron).
This generated a 0.1 rating, since 0.1% of the possible 2.2m households in what is considered the 20-county local market watched the game. Seeing as how only 40% of those 2.2m households can actually get CSN Houston, that's 880,000 households. Still, 2,200 out of 880,000 is not good, but it's at least a 0.25 rating. But yeah, not good.