I bet they set the machines up to make 500-round batches, but never got more than 440 good rounds out of any batch.
There's no accounting for Commie-block inefficiency or economics.
According to National Geographic, there's a thriving black market in burned out light bulbs. People buy them to substitute for the good ones they steal from work or the public areas of their apartment buildings.
Really.
Really. No bull.
John