Doubt on pg_timezone_names and pg_timezone_abbrevs

Hello PG members,
I used 'IST' in a query like this - * (timestamp_hour) at time zone 'IST'
time_ist *and did not get the expected output - timestamp in Indian
Standard Time. So I queried the 2 views that provide timezone info and did
not really understand the abbrev column.
select name, abbrev, utc_offset from pg_timezone_names where abbrev =
'IST' ;
name | abbrev | utc_offset
---------------+--------+------------
Eire | IST | 01:00:00
Asia/Kolkata | IST | 05:30:00
Asia/Calcutta | IST | 05:30:00
Europe/Dublin | IST | 01:00:00

select * from pg_timezone_abbrevs where abbrev = 'IST' ;
abbrev | utc_offset | is_dst
--------+------------+--------
IST | 02:00:00 | f

This is PostgreSQL 13.15 on AWS RDS. We have the same abbrev for 4
timezones in pg_timezone_names.
Regards,
Jayadevan