Ask HN: What do claims like product X is used by 90% of "Top" companies mean?

A lot of software products have claims similar to "Our product is used by 90% of the Forbes 100 companies" (or some other metric or grouping of companies) It sounds fairly straightforward. It is used by some minor players and big players and everything in between. Quite often if you keep an eye out on the ads, companies are listed as using several competing products. (Per different ads from different software vendors) What is the minimum requirement to make such a claim? If I wanted to claim that the 80% of the Forbes top 50 use my software what is a qualifying metric? One person downloading a demo one time? One person downloading a demo and a salesperson talks to them? One person downloading it and purchasing it? One department starts using it, even though other departments use the competitor? Or is it mostly just bllsht? (as most ads are). Sometimes I feel like calling the companies and asking them if and how they use whatever someone claims.