from this Brazen Careerist article:

“Recruiters check for inconsistencies. An experienced recruiter has seen thousands of resumes and spoken with countless candidates throughout their career. They know when something doesn’t add up. After scanning and shortlisting your resume, they will go through it with a fine-tooth comb to ensure there aren’t any discrepancies.”

So what kind of discrepancies and red flags do we notice? 

That's good advice. Attention to details matter.