here is a solution I found to this problem:
the first step, after opening the original image, is to select on the left panel, with the left mouse button, the area you like to enlarge, clicking outside the square and dragging the mouse, then adjust the size on the right panel with the zoom, apply the filters, calculate and exit.
In other words, the image you get is the one on the left panel, the one on the right is only a detailed view.
However in my opinion the program has a problem; I open a file, e.g. Photo1.jpg, apply some filter and I see in the bottom left row the name of the output file Photo1_e.jpg, then I press Calculate and the name of the output file become Photo1_e0,jpg, but when I exit in the output directory I found only the "intermediate" file Photo1_e.jpg (not enlarged) and the "final" file Photo1_e0.jpg is lost.