3rd Kyū

Conversely, when the file value is greater than the rank value, tracing down-left (↙) hits the 1st rank (bottom edge) first.

For example, consider a bishop on f4. The file value is 6 and the rank is 4.

The maximum steps down-left is "rank value - 1" = 3. Subtracting 3 from the file gives 6 - 3 = 3, so the starting point is c1.

When the file and rank values are equal, tracing down-left (↙) reaches both board edges simultaneously, so the starting point is always a1.

This is the a1-h8 main diagonal.