Postgresql- Explaining a Postgresql code in words

Explain in words what it does, and what the possible output values are for the
column it produces. Do you think that this query will achieve its intended result?

, case when i.time_at_job IN ('6_m', '6', '1_to_3_months') then 0
when i.time_at_job IN ('6_months_to_1_year', '1_year_to_', '7_months_to_1_year',
'1_y') then 1
when i.time_at_job IN ('1_year_to_2_years', '2_years', '2 years') then 2
when i.time_at_job IN ('2_years_or', '2_years_or_more','more_than_2_years') then 3
when i.time_at_job ~ '^[0-9]+$' AND (i.time_at_job::integer >= 60 OR
i.time_at_job::integer < 12)) then 5
when i.time_at_job ~ '^[0-9]+$' AND (i.time_at_job::integer >= 5 AND
i.time_at_job::integer >= 12 then round(i.time_at_job::float / 12)
when i.time_at_job ~ '^[0-9]+$' AND i.time_at_job::integer < 5 then
i.time_at_job::integer
else NULL end as time_at_job