When I copy/paste the solution code on Firefox and Chrome, I get the correct answer. On your screenshot it looks like the width of the box is wrong. Did you test some changes in the DevTools and forgot to remove them? Could you please reload the page without cache (CTRL+SHIFT+R) and copy/paste the code again? Which browser and OS are you using?
could you create new browser profile and try again if it work then either the issue
with one of your extensions disable all of them then re enable one by one till you get the one causing the issue
issue with cache clear your browser cache try to use longer time period
issue in the profile not sure how to fix this
if that not the cause could you right click the box then inspect and check what the width of the box and the h2 element the browser report
what is your screen size and resolutions