APEX

select distinct status,count(*) col1
,sum(
case
when reviwe_status='Y' then 1
else 0
end
) number_reviewed
from temp1
group by status
;

Hi,
SUM (CASE ...), as Bede showed, will work. You could also use COUNT (CASE ...), like this:

SELECT    status              -- or  LOWER (status) AS status
,         COUNT (*)  AS col1  -- or a more descriptive name, like number_total
,	  COUNT ( CASE
	  	      WHEN  review_status = 'Y'
		      THEN  'OK'
	  	  END
	  	)    AS number_reviewed
FROM      temp1
GROUP BY  status
ORDER BY  status  -- or whatever
;

If you really want to display 'open' and 'close' even though the table has 'Open' and 'Close', as you said, then you just need to change the first line.
In any event, you don't need "SELECT DISTINCT". The GROUP BY clause guarantees that status will be distinct in the output