Soy sauce varieties
I'm not as familiar with Japanese soy sauces as I am with Chinese soy sauce, but it's best to use light when called for.
Comparing light soy to dark soy is like honey to molasses; different taste, colour and consistency. Light soy is most generally used for cooking and dipping and sauces, whereas the dark is best for stews, braises or marinades with deeper flavour.
That said, I'd assume a general purpose soy from Trader Joe's to be a light soy. (No TJ's in Canada so I can't be sure.)
A light soy sauce tends to be somewhat thinner, lighter in color, and somewhat saltier than standard or dark soy sauce.
Some Japanese style brands, like Kikkoman, can substitute for a light soy sauce in some recipes.
So it pretty much depends on what your recipe is and whether the Trader Joe's is a light, standard, or dark sauce.