Question about castsequence under 6.0.2

I am a bit confuzzled about /castsequence now

Does it advance per keystroke or per activation?

So: /castsequence=x,x,y,x,x,z,x,x,y,x,x,z

if I spam 5 keystrokes a second and gcd is 1 second(for example) will it cast x, ignore 4 clicks (b/c of gcd) then cast x, ignore 4 clicks (again), then cast y and so on?

Or will it try and cast (0ms) ‘x’ (success), (200ms) ‘x’ (fail), (400ms) ‘y’ (fail), (600ms) ‘x’ (fail),(800ms) ‘x’ (fail), (1000ms) ‘z’ (success), (1200ms) ‘x’ (fail) etc?