How to change the effect speed of the fade animation in a Pro Gallery slideshow?

How to change the effect speed of the fade animation in a Pro Gallery slideshow?
I have the images set to change in a fade right now.
What I want to change is not the stop time per image,
but the time of the fade effect when the images change,
and I want this time to change more slowly.
I want to slow down the speed of the fade animation,
not the stop time per image.

Changing the speed will not work with the settings shown in the following image.
Can I write code in Velo to change this?