this, as is, can be triggered if one person clicked the same link twice (not what you're looking for). I think it'll need to be built out a bit deeper.
I can't think of a good way other than creating a SC for each email and ANOTHER set of SCs for each link IN each email (can be a lot if you track multiple links per email). Then allow the person to only run through each SC once (preventing opening and clicking the same email & link combo from firing success). The flow step would be 'change score' and have a Nurture Score field created so each time there's +1. Then trigger a master SC to check for score when it reaches 4 and then trigger.
I agree with Nelson. Another thing I would suggest is to be very careful with the use you make of Advanced Filters (they are not shown in the screenshot). When using Triggers they work a bit differently.