fix defaults

app.py

@@ -109,8 +109,8 @@ with gr.Blocks(css=css) as demo:
                 steps = gr.Slider(label="Steps", value=50, minimum=2, maximum=75, step=1)
 
               with gr.Row():
-                width = gr.Slider(label="Width", value=512, minimum=64, maximum=1024, step=8)
-                height = gr.Slider(label="Height", value=512, minimum=64, maximum=1024, step=8)
+                width = gr.Slider(label="Width", value=640, minimum=64, maximum=1024, step=8)
+                height = gr.Slider(label="Height", value=640, minimum=64, maximum=1024, step=8)
 
               seed = gr.Slider(0, 2147483647, label='Seed (0 = random)', value=0, step=1)