The label looked like it was printed on a cheap ink jet printer. The colors on the label weren't the right shades either.
The strings were guitar strings rather than cello strings. They're too short for a cello. The winding metal is different too. A bow doesn't grip guitar strings as well.
Most counterfeiters send super cheap cello strings with a fake label. In those cases, the best way to tell is that the silk windings on the strings will be the wrong colors.
There's a huge difference in sound. Cheap/fake strings tend to sound metallic and harsh. They also tend to break quickly, while a proper set of strings can last over a year.
