Usually 1 job means 1 person-year worth of work. So 6.5 years of a tech worker would usually mean 6.5 jobs.
The jobs also tend to include things like construction workers, etc. So if you hire 500 people to build the place over 2 years that's 1,000 jobs created.
That's before other taxes, like property (directly or indirectly through rent), sales, etc.
They don't need 25k jobs to support AWS clients in NYC. It's not like they're supporting on-site installations.