"Actuarial" is an adjective and refers to the types of activities that an "actuary" would do. An actuary is a person who calculates statistics around human health and length of life. So calculating life expectancy would be an "actuarial calculation". I hope the answer wasn't just adding more confusion...!

It means “relating to what an actuary does.” An actuary is a person who uses math and statistics to predict risk and help companies — particularly insurance companies — set their premiums at the correct level to make sure that the company can pay claims and still make a profit. Examples of use: “Actuarial calculations show that the company needs to raise premiums by 10% in order to cover the cost of paying claims.” “Actuarially, the life expectancy of a 52 year old man in the US today is 32.6 [more] years.”