I think you're still a bit confused. 81.8% refers to, out of the population which _both_ failed in their first suicide attempt, _and also_ eventually (within the study observation window, i.e. 3-25 years) dies of suicide, the proportion who die within year 1 rather than years 2-25. In fact, the study authors point out that they found follow-up attempts _less_ likely to succeed compared to the initial attempt:
> Of the cohort, 3.2% (48/1,490) died on index attempt, whereas only 2.3% (33/1,442) of index attempt survivors went on to kill themselves. This drop in the suicide rate for survivors compared with those dead on index attempt held true for both men and women (males: from 6.7% to 4.8%; women: from 1.2% to 0.9%).
> Of the cohort, 3.2% (48/1,490) died on index attempt, whereas only 2.3% (33/1,442) of index attempt survivors went on to kill themselves. This drop in the suicide rate for survivors compared with those dead on index attempt held true for both men and women (males: from 6.7% to 4.8%; women: from 1.2% to 0.9%).