Pick one variable, and shift it slightly.
For bitter, I usually pick grind weight. So, if you're putting 18g in, try 18.5g, but keep output the same. If adjusting the input, I usually adjust by 0.5g increments, then fine-tune as needed.
If you'd rather adjust the output, then adjust only that. So, using our example above, keep input at 18g, but decrease the output a measurable tad. If adjusting output, I usually adjust by 1g increments, then fine-tune as needed.
Generally, I'd rather adjust input, because output is sometimes harder to fine-tune.
You're fucked.... on the molecular level lol