The x/y axis on the micro:bit board follows display coordinates. This is a common format in programming where the x/y axis starts at the top left-hand side of the board. The pixels are counted from 0 from this point.
The 5 LED lights along the horizontal line of the display starting from 0 is the x axis.
The 5 LED lights along the vertical line of the display starting from 0 is the y axis.
There are a total of 25 LED lights that make up the display coordinates.
As the micro:bit board LED’s are for images and lettering, the board follows the display format. The micro:bit board x/y orientation is not for graphing data purposes and therefore do not follow the x/y graph orientation (which is common in Mathematics) where the x/y axis begins at the bottom left-hand side.