Thread:Gig218/@comment-22439-20150108102725/@comment-25806814-20150126073651

The 75% thing is not about number of map you have to clear, it is the win rate of you sortie.

Like if you are force to retreat before reach the boss because your flagship got heavy damage then that count as 1 sortie lose. You can keep track of it in your Admiral page http://kancolle.wikia.com/wiki/Tutorial:_FAQ#What_does_the_admiral_stats_page_show.3F

And keep in mind that send SS to 2-4 might decrease your win rate (a lot if you are unlucky)