You're right, the mistake I was making was not realising that the calculation was for leased office space as an entire industry, rather than as their plausible

You're right, the mistake I was making was not realising that the calculation was for leased office space as an entire industry, rather than as their plausible potential customer base. Since their actual market is more niche (in practice it seems to be satellite offices, startups and remote workers) than general commercial office space, I'd still propose that it's significantly overstated, but thanks for the correction regardless.