Comparing Time

I am creating a puzzle game with 90 levels. Each level Has a stopwatch (Below) which tracks the time. Since sec min ext are separate variables and the time is displayed in a String, I don't know how to compare current time with a saved best time.

   var sec : float = 0;
   
    var intsec : int;
    var minutes = 0;
    var seconds;
    var miliseconds : int;
    var guiTime;
    var time : String;
    var startTime;
    var timerShow : boolean = false;
    var startTimer : boolean = false;  
    var BestTime = 0;
   
   function Start(){
      startTime = Time.time;
   }
   
   
   
   function Update() {
           if(Input.anyKey || startTimer == true){
                  startTime= startTime-Time.time;
               startTimer=true;
                       
            sec = sec + Time.deltaTime;
            intsec = sec;           
            miliseconds = (sec - intsec )* 10; // Here you can use 10 instead of 100.
            
             if(intsec < 10){
                  seconds = "0"+intsec;
             }
             else{
               seconds = intsec;
             }
    
           if(intsec >= 60){
                  minutes++;
                 sec=0;
             }
    
           time = minutes + ":" + seconds + ":" +miliseconds;
    
        }
   }
 
 function OnGUI() {
               if(Input.anyKey || timerShow == true){
               timerShow = true;
             GUI.Label (Rect (10, 10, 100, 20), time.ToString());
   //          GUI.Label (Rect(10,30,100,20), BestTime.ToString());
            }
    }