Variable keeps value after closing app

Hello, I have spell cooldown variable :

     private float nextFire = 0;
     public bool IsOffCooldown()
     {
         return Time.time > nextFire;
     }
 
     public void Cast(Transform spellSpawnerTransform)
     {
         nextFire = Time.time + FireRate;
         Instantiate(t$$anonymous$$s, spellSpawnerTransform.position, Quaternion.identity);
     }

once i close the app the variable nextFire keeps it's previous value i.e if the last time the game went on for let's say 30 secs the nextFire variable will have 30f as starting value. Why ? How to fix t$$anonymous$$s ?