Alex - I know. This is aggravating when specific instructions aren't provided.
One of the issues would be if it's an amino acid supplement. In that case, the recommendation is away from meals so that the aminos in a meal don't compete or overwhelm the supplement aminos. Taurine (a non-essential amino acid) is an exception in that it's recommended with meals to avoid stomach irritation.
Other times, the concern is that with meals, the additional stomach acid destroys the nutrient; conversely, in other cases such as minerals, stomach acid is a good, necessary thing.
Sometimes taking with food becomes important because on an empty stomach, some vitamins or minerals can cause nausea.
No instructions? Try a Google search on the specific nutrients involved to see if you can learn what's needed for efficient metabolism.
Jackie