fgl_getwin_x() returns the column at which the currently active 4GL window was drawn:
OPEN WINDOW w_test AT 3, 2
You have opened the window at column 2. For this window, fgl_getwin_x() would return the value 2.
fgl_getwin_y() returns the row at which the currently active program window was opened:
OPEN WINDOW w_test AT 4, 5
The window is opened at row 4 of the 4GL screen. In this case, fgl_getwin_y() will return 4.