Warning, this is not a real math explanation. It's just a bunch of words and numbers.
Imagine a grid of squares, each representing a pixel. The 4-3 pattern is a series of instructions that tells you when to draw a line between two squares.
Start at the top left corner. If the current square's number is divisible by 3, draw a line to the right. Otherwise, draw a line down.
Repeat this process until you reach the bottom right corner.
Example:
| 1 | 2 | 3 |
| 4 | 5 | 6 |
| 7 | 8 | 9 |