I have working code that counts down, but it is from 0. I want to try and get millus() to start at 20 instead of 0 as my game has a time limit. Is there a way to do this?

Thanks

2. 
   
3. 
   
4. //Timer Variables
5. int m; 
6. int starttime;
7. int seconds;
8. 
   
9. void setup() {
10.   
11.  size(600, 600); 
12. }
13. 
    
14. void draw() {
15.     background(255);
16.   //Milliseconds time counter converted to Seconds
17.   m =  millis();
18.   seconds =  -m / 1000;
19.   
20.   // when game started make timer 20  
21. 
    
22.     starttime = 20 + seconds;
23.   
24. 
    
25. 
    
26.   //Display Timer
27.   fill(0);
28.   textSize(50);
29.   text(seconds, 80, 80);
30. 
    
31. }

2. int colour = (int) random(3);
3. 
   
4. int rectcolour;
5. 
   
6. void setup() {
7.   
8.   size(600, 600);
9.   rectMode(CENTER); 
10.   smooth();
11.  
12. }
13. 
    
14. 
    
15. void draw() {
16.   
17.   switch(colour) {
18.     case 0: 
19.       fill(255, 0, 0);
20.       break;
21.     case 1: 
22.       fill(0, 255, 0);
23.       break;
24.     case 2: 
25.       fill(0, 0, 255);
26.       break;
27.   }
28.   
29.   //rect(width/2, height/2, 200, 100);
30.   
31.   fill(255, 0, 0);
32.   rect(125, 525, 100, 50);
33.   fill(0, 255, 0);
34.   rect(300, 525, 100, 50);
35.   fill(0, 0, 255);
36.   rect(475, 525, 100, 50);
37.  
38.   
39.   
40.   rectColour;
41.   rect(width/2, height/2, 200, 100);
42. }
43. 
    
44. void mousePressed() {
45.   if(mouseX > 0 && < 300) {
46.     rectColour = fill(0, 255, 0);
47.   }
48.   if(mouseX > 300 && < 600) {
49.     rectColour = fill(0, 0, 255);
50.   }
51. 
    
52. }