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I think you do understand the gates, I think you were just having some trouble with the output count of the recipe.
So the fuel pellet recipe outputs 2 and not 1, that means that the gate will be open long enough for 2 items of porcelain to go through at that belt speed. You can fix this by making the output belt twice as fast, or by making a splitter setup at the output belt, so that the gate detects half the number of items.
I would also advise you to make the output belt longer, so that you don't get weird timings and stuff. If the funnel is trying to place items where the gate is detecting, it could result in the belt only detecting "half" the item, meaning that it doesn't detect the item's full passage, and it could result in the gate staying open less than it should.
i ve tried that, get rid of funnels, set new conveyer, made conveyer x2 speed ( i ve tried that before, but with funnel) and... it still sometimes messes up because logic gate let 2 glowy things through. I have no idea how, but this is really uncomfortable. But it definetely works better now, now it takes more time for it to completely stop working.
122 days ago (+1)
splitter version. Partially worked i think. Now there goes only 1 glow. but 2 starch instead of 3. UPDATED. I set speed to green(x4) and it started working as was planned. I have no idea why. 
It's good you got it to work.
I tried to replicate your setup, and it seems to work without a splitter as well:
Both of the gates are taking the same point on the output belt as source. The output belt is at 2x speed, the porcelain belt is at 1x speed and the starch belt is at 3x speed. I ran the setup for 100 recipes, and it didn't seem to jam for me.
Btw, congratulations on automating nuclear fuel!
122 days ago(+1)
Updated2. Sometimes autocraft still fails. I just looked and craft isnt going, there is no glowy glazed parcelain in press. Which means that in one moment logic gate bugged and everything turned off.
From what I have tested when playing, and even before I released the game, the logic gate was pretty solid. The code is simple and it's probably not what is causing the problem. If you want to, you can send me the save data (either upload it here if it works, or on discord), that way I can look around and see what the problem is could be.
You can also add me on discord, that way I can help you easier. Discord: kittykillerkuriosity