You're right. USPS employment is now closer to 350,000.
Imagine that. Fake news.
I took the 650,000 from a statement in the article:
“The Postal Service, which employs 650,000 people, is asking for $75 billion in aid from the government, and, according to The New York Times, another $14 billion to pay off debt related to a retirement benefits program - a whopping $89 billion total.”
Article is wrong I guess.