The protein powder says 25 grams per scoop. Usually that is true in the way you mean it. Sometimes it is only true in the way a lab test means it, and the difference has a name: protein spiking.
How the trick works
The standard test for protein content measures nitrogen, because protein contains it. But cheap free-form amino acids contain nitrogen too. A manufacturer can add inexpensive fillers, and the tub tests at 25 grams while delivering less of the complete protein your body actually uses. The label passes. Your muscles keep score differently.
Why you cannot catch it at the shelf
Nothing on the front of the tub distinguishes spiked from honest. The evidence lives elsewhere: independent lab results, class-action filings, FDA warning letters. All public, all scattered, none of it cross-referenced against the product in your cart by anyone, least of all at the moment you are deciding.
What helps
Read the amino acid profile if the brand publishes one; honest brands tend to. Prefer products with third-party certification (NSF and Informed Choice are meaningful in this category). Be suspicious of prices dramatically below the market for the same claimed protein content, because protein is expensive and deep discounts have to come from somewhere. And check when the product's reviews were written, since spiking scandals tend to show up there before anywhere else.
The bigger pattern
This is the same story as fake discounts: a claim you cannot verify at the moment of purchase, and evidence that exists but is not in front of you. Reading that evidence for you is the job we are taking on, starting with Amazon prices and expanding from there.