“In the time of Ahasuerus” or “When Ahasuerus was ruling as king”
This is background information to help the reader identify Ahasuerus. (See: rc://en/ta/man/translate/writing-background)
“one hundred and twenty-seven” (See: rc://en/ta/man/translate/translate-numbers)
A “province” is a large area into which some countries are divided for the purposes of government.
Here “royal throne” may refer to his rule over the kingdom. AT: “ruled the empire” (See: rc://en/ta/man/translate/figs-metonymy)
This refers to a castle, stronghold or fortified city.
This was a royal city of Persian kings. (See: rc://en/ta/man/translate/translate-names)