It was ambiguous, but he compared the wasted time (time wasted at work while working for a bad company) to the total time you have in your working life. He says you spend 21%-35% of your time at work, so during that 2 years you'd spend .42-0.7 years working. And if you calculate with 40 years of work life, then it comes to about 2% of that time.
That might be what happened. The reason it's unsound is, the numerator is in actual time spent at work and the denominator is in total elapsed time including non-work.
