Panel 2: "Paint By Numbers" refers not to the tacky do-it-yourself cheapo masterpieces from childhood, but to these neat puzzles where you create a picture in a grid, using a set of numbers around the edges as a guide. Here's an example of a finished Paint By Numbers puzzle:
If this were presented as an unsolved puzzle to work on, the grid would be empty with all white squares. The numbers work like so: Each row and column is to contain one or more lines of black squares, individually unbroken but separated by white space. The numbers correspond to the unbroken lines of black squares. (Er, just study the diagram. This is one of those things that's easier to show than explain.) So anyway, you start with an empty grid and use the numbers to figure out which squares to fill in black, and eventually you end up with a ducky or some other picture.