in a UNION query, the result set is actually a table, and this table's column names are taken from the first SELECT in the UNION
so you could add a literal to each SELECT, e.g.
SELECT SUM(CountOfCity1) AS total
, 'New Listings' AS totaltype
, 'New Pendings'
, 'New Closed'
note you did not need DISTINCTROW because each of your SELECTs is producing only one row (the one with the sum on it) so of course it's gonna be distinct