When using auto increment with write cell, does this increment the write from cell, write to cell, or both?

I know I can add symbol to stop a cell from autoincrementing, but if I leave out symbol do both fields or just one field autoincrement?

In my testing it seems like only write to increments, but I want write from to increment.

This increments only the destination cell and it is meant to be used inside a ForEachRow activity. The From field is using the Current Row, so it will go through all the rows in the range.