I'm trying to apply a rule-based approach to my data that considers both the positive or negative value and the value per se (from -66 to 77). I was able to apply a rule for negatives/positives (red and green, respectively), but how can I add the rule for symbol size considering the size of the number? (e.g., a value of 10 would have a bigger point symbol size than a value of 5).

What I did so far:

negative: "diff" < 0 positive: "diff" > 0 neutral: "diff" = 0

I'm trying to do this for a point vector (I can't upload an image here; the server is bugged)