Yeah these things aren't designed to cool things down, they're designed to take something that's already chilled, but in an inconvenient location (such as in your kitchen, past a sleeping infant), and keep it cool in a more convenient location (your home office).

Anyway if you want to check your math, I did a quick experiment. My fridge cooled a 1.5 liter bottle of room temperature (25.6 C) tap water to 18.4 C in one hour, and 11.9 C in 2.