In a vulnerability assessment report, the "exploit" field is used to indicate whether or not a particular vulnerability can be exploited, or used to attack the system. The "Yes" value in this field indicates that the vulnerability can be exploited, while the "POC" (Proof of Concept) value indicates that a proof of concept for exploiting the vulnerability has been developed, but it is not known if the vulnerability can actually be exploited in a real-world attack.
So the correct remediation priorities should be:
1) Server2
2) Server3
3) Server1
4) Server4