When it comes to SE RNG, the number stated meant nothing unless it says 100%

Because in bad days, you can still botch 10 out of 20 desynthesis where the success rate is well over 80% lol

I remember my first weapon took some time, but the 2nd weapon was insanely fast because I got half of the Atma back-to-back within 10-30min time frames.

RNG.