Why my images size(bytes) becomes bigger after upload to magento?

[DaveShot]

Hi! my store is VERY slow. Investigating the causes I discovered that my product images is 4x bigger from the original uploaded image.
Example: The original uploaded image has 100px but the image displayed at view page has 400px
I downloaded this image and the size is the same, 800x1200px

Someone has any idea what is causing this problem?
My magento is 2.4 and I not change any default configuration about image size and image quality

[Sanjay Jethva]

@DaveShot  Please check the product image size in
app/design/frontend/ThemeModule/ThemeName/etc/view.xml
The image size which is set in this file will display on the frontend.

[DaveShot]

I checked this file, but I don't identify nothing "wrong". I forced some options to use exactly my default size 600x900 or small size 400x600 or large 800x1200 and there was no result at front end.

At Images Upload Configuration, I changed Quality from 100 to 80 allow resize "Yes" and after clear all store caches the size appears to be right now.

I thing that problem was related to quality 100% but I don't know exactly what was the problem..

thank you