Here's how it works as I understand it:
Current Piracy is the raw amount of piracy occurring, before taking into account any suppression or starbase effects.
Current Piracy + starbase and suppression effects = Piracy Effects, which cannot be greater than the Max Piracy value.
Max Piracy relates to Piracy Effects, not Current Piracy.
Edit: I'm not sure how Piracy Suppression factors in. The piracy effects of -172.99 comes from current piracy + starbase protection. The 20 value for Piracy Suppression doesn't seem to figure in on this screenshot. If I had to guess, I'd say it might lower the Max Piracy value, but without looking at the code or testing I can't be sure.