I just found this signal decoder for the "Ceto System".

It comes with the following modifiers:

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WEALTHY FOES
Enemies drop lots of credits upon death. |-30%

Loot Quality: -30%

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This seems odd. It says enemies would drop more money, but the money modifier denotes a negative.
Due to the negative loot modifier, this signal decoder offers up nothing but negatives.

I do not know whether this is a display bug, or an actual issue with the decoder modifiers.
I made a savefile where the decoder is in the ship's hold, should there be any need for it.

Enemies in High Risk Areas usually drop nothing, only the boss does.
The "Wealthy Foes" modifier is an advantage for you, so to balance this, the loot quality the boss drops is reduced by 30%.

That's how I understood the mechanic.
Later on there are other negative modifiers, like allied fighters. And more than one of those can appear on a signal decoder.

The weird thing is that this thing claims to reduce credit rewards. If that means that it allows for 70% of credits to drop, then I completely misunderstood it, meaning it isn't clearly conveyed.

But thank you very much for the explanation!

I think I was also a bit confused by the decoder items at first.

The percentages beside the modifiers just add up to a global value that impacts the loot dropped by the boss.
Attached screenshot of a more advanced area. There are positive, negative and neutral modifiers.