The Entire Bolivian Army?

Why do people say that the movie has Butch and Sundance fighting the entire Bolivian army?

Why would the entire Bolivian army be near to such a small Bolivian town? Maybe they were on maneuvers near the town.

But it didn't look like the entire Bolivian army of thousands or tens of thousands of soldiers was present. It looked to me like one troop of Bolivian cavalry was summoned to the town.

Don't moviegoers know how to count? If typical moviegoers couldn't tell the difference between tens of soldiers and thousands of soldiers, it's a good thing they weren't military scouts!