Valve says "the Steam Machine is equal or better than 70% of what people have at home," but I feel like that's missing the point

Before you start making plans to evict your current rig, I want to explain how the Steam Hardware Survey actually works. Rather than representing every player that uses the storefront, the monthly census instead uses a small percentage of participants who've opted in as a sample. It's anything but representative of all 154 million active users, meaning the statistic above isn't an absolute.

Does the author know how *survey sample sizes work?

Do I?

Is it because it's opt in or opt out?