The Loop is what repeats itself over and over again until "d" is equal to 46. Everytime through the Loop, "d" is increased by 1. As soon as "d" equals 46, the Loop stops playing and the movie continues to the next frame. The next frame (Frame 2) in this example has a "stop" command found on the Image Layer. What follows is what happens. Though it may appear as if the boxes appear all at the same time, they are technically produced and placed one at a time. (A better understanding may be gleaned from the Appearing and Disappearing Solar Boxes Tutorial.)

The first If statement in the Loop action tracks the position of the newly duplicated "box"&d instances. Written out, you have "If (GetProperty("box"&d, _x)> squares*sizex + origx - 5" where "squares" is equal to the number of boxes you want across the screen and by subtracting 5 you don't create an extra box. As soon as the x position of the new instance is greater than the x position where you would prefer to have a new line start then the new instance is placed on the next line to continue covering the screen with boxes in an orderly fashion.

The Set Property commands below the first If statement places the new "/box"&d instances on a new line. It places the new instance back to "origx" and the new y position becomes "origy" plus "sizey", or directly underneath the initial "box" instance. The remaining If statements control the placement of the boxes on the screen. Where we find "n" being used, the new box instances are placed one next to another across the screen, as long as "n" is less than the number of "squares" you want across the screen. As soon as "n" becomes greater, the "else if" statements begin. "ntwo", "nthree", "nfour" are variations on "n". And so it continues until 46 box instances have been created ("d" = 46).

The number 46 derives from what the example needs to cover the space. With 9 boxes across and 5 lines high, as soon as "d" equals 46, the program can then continue to the next frame, where there is a "stop" command.