Taking google's answer for things they're calculating with math is probably safe, but if you get into the habit of reading google's answers to queries it will have you believing a lot of nonsense because many of the answers google offers are not calculated at all, but instead are regurgitated nonsense that google read on the internet and took at face value (example from Technology Connections: https://youtu.be/TbHBHhZOglw?t=58)
I assume the GP is referring to the instant answers it gives you in a white box separate from search results. In this instance it is calculated by google and not crawled from the web.
Those instant answers are the ones I'm talking about. Sometimes they're calculated, but often they're regurgitated from web crawls and the UI doesn't clearly differentiate the two.
