Forum members in the US will hopefully pick this up as their expertise on FDA requirements is vastly greater than mine, but I presume you're referring to the exemption from ordering by proportion that can be applied below 2%, as included in 21CFR101.4:
(2) The descending order of predominance requirements of paragraph (a)(1) of this section do not apply to ingredients present in amounts of 2 percent or less by weight when a listing of these ingredients is placed at the end of the ingredient statement following an appropriate quantifying statement, e.g., "Contains _ percent or less of ___" or "Less than _ percent of ___." The blank percentage within the quantifying statement shall be filled in with a threshold level of 2 percent, or, if desired, 1.5 percent, 1.0 percent, or 0.5 percent, as appropriate. No ingredient to which the quantifying phrase applies may be present in an amount greater than the stated threshold.
There is a general FDA page on labelling and nutrition guidance on their website here that might be useful to you: https://www.fda.gov/...ory-information