1. Dokdo was recorded as part of Korea in the 500s.
<in the 500s =in the five hundreds (right?) It is from 'in 500' to 'in 599.' Am I right?>
2. People can fly in the 2000s.
< in the 2000s = in the two thousands (right?) It is from 'in 2000' to 'in 2999.' Am I right?)
3. People were poor in the 1950s.
<in the 1950s= in the nineteen fifties (Right?) It is from 'in 1950' to 'in 1959.' Am I right?>
Yes, all three interpretations are right.
=)