This is the cumulative amount of extras unlocked.
to see your current status, go to lumi's darden and hit Y, then Y again. this shows you your stats screen. upper rightside percentage is what you want to get over 75%
it helps to have cleared all stages on normal mode, but the main percentage you'll get out of the art gallery.
this is under menu - extras - art gallery.
there are twelve pieces of art for each of the five levels.
each of them has a particular requirement.
-clear the archive
-clear all areas with a purification rate of 80% or above
-clear all areas with a purification rate of 90% or above
-clear all areas with a purification rate of 100%
-achieve more than 20 perfect octa-locks
-achieve more than 50 perfect octa-locks
-achieve more than 10 consecutive perfect octa-locks
-collect all items in the archive
-complete the archive without sustaining any damage
- -stage related quest-
- -stage boss related quest-
-clear the archive with a 5 star clear ranking (800k+ points)
most of those will come as you play normally.
the 100% ones you'll get when you try for those respective achievements.
the octa-lock ones you might have to work for, or will achieve when you go for the 5 star clear.
the stage related quests can be easy or hard, depending on your skill (i find octo-locking the butterflies in stage 3-1 to be very tough, thanks to one of them being very close to other enemies).
it doesnt matter if you do these on normal or hard, but 'free eden' mode unlocks nothing.
good luck. this is an achievement you can clear while working with many others, such as:
The Genius Play achievement in Child of Eden worth 178 pointsClear the Matrix Archive on Normal Difficulty Mode and achieve 100% purification. The Pulse-Pounding achievement in Child of Eden worth 132 pointsObtain more than 800,000 points in the Matrix Archive on Normal Difficulty Mode.