Slider Image problem

Hi guys,

I have this problem:

I created a 800x440px picture and after performing lossless compression on it, the file size is 44kb.

So I upload it to WordPress and use the slider shortcode provided by this plugin.

I also set the slider dimensions to exactly 800x440px, which is the size of my picture.

However, the result is this:

Due to the specified slider dimension, the plugin resizes my image again to 800x440px, even though my pic is already 800x440px.

This creates a larger image which is 57kb.

My questions are:

1. Why doesn’t the slider use my image? Instead it has to resize the image by itself.

2. How can I make the slider use my smaller image and prevent it from resizing?

Thanks in advance

https://ww.wp.xz.cn/plugins/shortcodes-ultimate/