Why a number rather than a description
CSP exists so a specification can be verified rather than argued about. Manufacturers publish a required profile for every product, and the scale is defined against physical reference coupons, so a contractor and an inspector can agree on whether a slab is ready without either one guessing.
Matching profile to system
A thin sealer needs very little profile. A standard flake or solid coating needs CSP 2-3, achieved by diamond grinding. A thick quartz broadcast or urethane cement system at an eighth to a quarter inch needs CSP 4-5, which usually means shot blasting rather than grinding. Over-profiling for a thin coating is as wrong as under-profiling for a thick one.
What the wrong profile looks like later
Under-profiled slabs produce coatings that lift in clean sheets with grey concrete on the back of the flake. Over-profiled slabs under a thin coating telegraph the grinding pattern through the finish, or leave pinholes where the coating could not fill the texture.
It should be on your quote
A quote that names a target CSP is a specification you can hold a contractor to. A quote that says the floor will be "properly prepared" is not. Asking for the number is the single most useful question a homeowner can put to a coating contractor.
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