The phrase "few milligrams" means a very small amount, usually referring to a measurement of weight. It is equivalent to a tiny fraction of something, like a few grains of salt or a few drops of water. Full definition
The Blend burger contains fewer calories, fewer grams of saturated fat and fewer milligrams of sodium compared to the standard burger for schools. (fb101.com)
Unlike with broccoli or strawberries, the extra nutrients in organic carrots aren't worth your while; there's so much vitamin A already that an extra few milligrams gets lost in a sea of clear skin. (supernaturalacnetreatment.com)
Then comes the «nerve - wracking» task of scraping off the calcite without marring the pigment, and the painstaking analysis of a sample of few milligrams. (sciencemag.org)