How to Shade Bids Randomly?

Bids are not random bids or something that the advertiser adds will welcome with the bits for each query. We still rely on the bids, but perturb them randomly. And if you shade bids in the right random way, you do better than ge this seemsa the onset, very surprising to me. If they're just random budgets, it seems like they wouldn't correlate with the true budget. So there's no value. There's no information there to work with. How does the randomization, how can i exploit that mathematically? Thethe bits t the budgets are unknown, and the bids are not random ones.