Why is it written in the properties that the container occupies 100% of the screen, but in reality it is much larger?

Question

css

Good afternoon. I am engaged in pre-adaptation of the site after the previous developer. I don’t understand what the hell is it, why does the container actually occupy more than 100%, although it is written in the properties that it should occupy 100%?
http://dna.ukr/domashnij-test/zakazat-dnk-nabor.html