Header image slider question

Hi
I am using the plugin Header image slider, i’ve changed the
#page
max-width: 1000px

to
max-width: 1200px

so when i insert a image to the plugin it dont adjust around the place it suppose to leaving some area white, im trying to find the option to change it to 1200px in the plugins css but cant find it?

here you have a exampel
https://screensnapr.com/v/ZhWyh4.jpg

Thank you!