I created a service of type "NodePort" and on describing the service - What does "unset" signifies. Please note I specified "port" and "nodeport" at the time service creation / update

Name:                     nginx-nodeport                           
Namespace:                default                                  
Labels:                   <none>                                   
Annotations:              <none>                                   
Selector:                 project=chapter3,service=web             
Type:                     NodePort                                 
IP:                       10.96.220.155                            
Port:                     <unset>  80/TCP                          
TargetPort:               80/TCP                                   
NodePort:                 <unset>  31634/TCP                       
Endpoints:                172.17.0.4:80,172.17.0.5:80              
Session Affinity:         None                                     
External Traffic Policy:  Cluster                                  
Events:                   <none>