This is how Chrome displays the “Cascading” part of “Cascading Style Sheets”. What the strikethrough means is that something with a higher specificity has overridden that style attribute. If you click on the “Computed” tab and look for the attribute you’ll see all the CSS classes that have affected it, and you can easily work out what is doing the overriding.
Also, that image isn’t really a lot of overrides. In a big app you should expect to be able to scroll that list a loooong way. It’s fine, and it won’t impact performance or SEO at all.