それらを1行の2列にしたい場合は、試すことができます
SELECT
(
SELECT COUNT(DISTINCT(nickname))
FROM capture_captive
WHERE `number_successed`> 0
) users_got_a_card,
(
SELECT COUNT(DISTINCT(`nickname`))
FROM `capture_captive`
) users_shown_captive
また
SELECT users_got_a_card, users_shown_capt
FROM
(
SELECT COUNT(DISTINCT(nickname)) users_got_a_card
FROM capture_captive
WHERE `number_successed`> 0
) a CROSS JOIN
(
SELECT COUNT(DISTINCT(`nickname`)) users_shown_capt
FROM `capture_captive`
) b
また
SELECT COUNT(DISTINCT(IF(`number_successed` > 0, `nickname`, NULL))) users_got_a_card,
COUNT(DISTINCT(`nickname`)) users_shown_capt
FROM `capture_captive`
これがSQLFiddleのデモです