n and m were results of weekdays with different orders of arguments. I've changed the names to weekdays_date1_date2 and weekdays_date2_date1.

when creating this kata, I thought about this and specifically created an edge case test to check this point. I, frankly, always myself thought that using between operator without casting date type will exclude last day from the boundaries. But I checked that both

select * 
from courses
where course_date between '2022-10-01' and '2023-06-30'
order by course_date desc

and

select * 
from courses
where course_date between '2022-10-01'::date and '2023-06-30'::date
order by course_date desc

are including 2023-06-30. so for sure there is no issue in the kata, but I am still perplexed why this is happening :)