That marks the median age of death, but I don’t think that’s the definition of life expectancy (though maybe the term is used loosely or imprecisely to mean the median age of death or the average (mean) age of death in different situations…). The definitions of life expectancy I found claim it’s the mean age of death, which would make sense because the expected value of a random variable is the arithmetic mean. That said, the median on the life tables that I have found seem to correlate much more closely to the age of 77 versus the life expectancy at birth which is much lower (78-79 for the median and 74 for the life expectancy at birth for 2020 data)… but the actual paper is behind a pay wall so I have no idea what they’re actually computing for 77 years of life expectancy… my guess is that it’s the median and not the mean, but maybe they’re considering people over a certain age or something… either way, the mean / median getting confused is an issue and I wish people were more clear about what metric is actually being communicated.