That's the average salary for a software engineer, not the median. Also, the SSA site uses "net compensation" for their numbers, which they define as "compensation (wages, tips, and the like) subject to Federal income taxes, as reported by employers on Form W-2" and "includes contributions to deferred compensation plans, but excludes certain distributions from plans where the distributions are included in the reported compensation subject to income taxes". It is not clear to me how that maps to salaries reported on Glassdoor.