that's what the Right() does. It takes the rightmost two characters of the string. So from 0 - 9, you get 00 - 09 and Right() simply takes those two characters. When you have 10-14, you get 010 - 014 and Right() will take the last two characters, ignoring the leading 0, so you're back to 10-14
Run this program to see it in action
Run this program to see it in action
For t = 1 To 14 Print "run_"+Right("0"+t,2)+".png" Next WaitKey()