Are you sure that is not Dust Extreme which is disclosed or their Cobra 6p Extreme? because even prior versions of Angel Dust had less like I want to say AMP Cit version ( 2nd version ) they told me 275mg or so in an email long while ago and the one before that orig 1,3 like 250 or so and the Dust V2 which was after they removed Amp Cit had 300mg.
Dust Extreme has 350mg ( just an increase of 50mg of caffeine over Dust V2 )
No version used 400mg to my knowledge