When you delete newlines below the cursor with the delete key, the cursor position (in terms of line number) does not change. However, the line number in the status bar does not reflect the same. It instead decreases by 1 as if the lines were deleted with backspace. This causes the line number to be out of sync of the actual cursor position, until it gets updated by another event (such as moving the cursor).

This is likely due to EditorState.apply_delete() treating all Delete events the same by decrementing primary_cursor_line_number by the number of newlines deleted.