HTML font-size: 62.5% is way larger than it should be

Hello, I'm running into a problem where I want to use rems as a unit, so I set the html font-size to 62.5%, which I've seen as a common practice, which should give me 1rem = 10px (because the default font-size should be 16px). But, when I go to use these newly set rems the styles on the page using them are larger than what they should be. For instance, I set a margin bottom to 8rem expecting 80px but on the page its displayed as 120px, walmartone despite me inspecting it with dev tools and it saying its using 8rem. I'm just so confused what could be making these rem larger than 10px / rem. I'm using Chrome if that matters. Any ideas? I know this is common practice.