How do colleges verify the information on your college app is true?

I’m seeing people on these threads with an absolutely ludicrous(ly impressive) array of leadership positions in extracurriculars, experience synthesizing monoclonal antibodies at local research centers, multiple internships, hundreds of relevant volunteer hours, national awards, etc., etc.

But when someone puts down that they volunteered for 300 hours at a local hospital, how do colleges verify that? What if someone only volunteered 30 hours and slipped an extra “0” in when no one was looking? What if you were involved in something that didn’t keep a ready list of its participants, and just let people come and help out/coordinate activities/events, and you put it down on your list of ECs when you perhaps only signed up online for the event but never attended?

Thanks in advance for the answers.

They don’t. They trust you and also don’t care about most of what you list. If it’s important enough to matter, it’s probably easily verifiable. 30 or 300 hours is meaningless

They generally trust students to put the correct information, but if something seems fishy they have ways of finding things out. Like they can call your guidance counselor if there seems to be a discrepancy, looking things up on the internet, or contacting the applicant themselves

Some of the really big stuff, like national championship in something, is likely to be on a web site somewhere and therefore quickly verifiable.