There is no specific grit to any of these polishes. (You posted in this forum and Brunswick's, at least)
IF a grit has abrasive in it, then the final finish will always be somewhat different depending on the starting surface, the type/brand of coverstock it is, whether it's pearl or solid, the amount of polish, the time applied the amount of pressure used.
Storm gives a "number" for Reacta SHine (1500) and Xtra SHine (3500) but that's no guarantee that every application wil wind up at that figure. It depends on all the above factors, plus probably several more. Those number are generic, generalized maximums, and nothing more.
There is no magic here, just common sense.
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"None are so blind as those who will not see."