It's easy to contextualize. 50 million human years lost means that people would have to put in 50 million human years worth of work to recover the economic loss of COVID-19.

Consider the average human worker. In their life, they will output around 10.5 human years worth of work. 50 million years represents the total output of about 4.76 million human lives.

So if you delete the production of 3 million people due to COVID deaths plus all the time spent in lockdowns, 50 million human years lost sounds about right, but probably could be higher. I'd say it's probably about 80 million human years lost.