Some Supplement Facts panels replace a list of individual amounts with a single line: a named blend, a total weight, and then a list of ingredients underneath with no individual quantities. This is a proprietary blend, and reading it well means understanding exactly what it does and does not disclose.
What it discloses is the total. The blend line gives the combined weight of everything in it. The ingredients within the blend are still listed, and by convention they appear in descending order by weight, so the first-named is present in the largest amount and the last-named in the smallest. That ordering is the only quantitative clue the format offers.
What it withholds is the split. You learn the sum and the ranking, but not how the total divides among the ingredients. A blend could be almost entirely its first ingredient with trace amounts of the rest, or it could be evenly distributed, and the label reads the same either way. The format is permitted, and its stated rationale is protecting a formula from copying. The effect on the reader is reduced visibility into individual amounts.
The phrase to flag is when a marketing claim leans on a specific ingredient that sits inside a proprietary blend. The ingredient may be named prominently in the copy while its actual amount is invisible inside the blend total. Being present in a blend and being present in a meaningful amount are different things the format does not let you distinguish.
The reading habit is to note the blend total, read the ingredient order for what little ranking it gives, and resist assuming any single ingredient is present in a particular amount. Where amounts genuinely matter to someone, the absence of a breakdown is a real limit, and questions about it belong with the manufacturer or a qualified healthcare professional. The label-reading point stands on its own: a proprietary blend tells you the sum, hints at the order, and hides the rest.