Suppose
X was 6 and the author believed there was a p1 > 0.2 probability of exiting for "twice £X million" and a p2 > 0.2 of being offered less than $2M for the acquisition.
This places the value of not selling at >= £2.4 million and the value of the sale at Then consider the opportunity cost of going to work for Google for a serial entrepreneur. There may be a 0.8 probability of $250k/year for four years. But that comes at the price of not developing a startup with the potential for a fuck-you money exit.
The hindsight we have doesn't include an assessment of the toll of relocating from the North UK to Silicon Valley with a spouse and children while leaving behind family, friends and community.
In the end, if you're looking for a $2,000,000 exit. You're not really founding a startup. There's nothing wrong with that. But "startup" in the sense that people like PG use it is not the right term.