What does this equation mean?

where N is the number of exercises targeted, $c_{\text{generate}}$ is the compute cost of producing one candidate item, $p_{\text{fail}}$ is the fraction that fail correctness or contamination filtering and must be regenerated, and $c_{\text{regenerate}}$ is the cost of another attempt. This is not drawn from a specific paper’s disclosed cost model — none of the sources here publish exact figures — it is included only because it makes explicit an assumption that is easy to gloss over in prose: a synthetic curriculum’s real cost is dominated by $p_{\text{fail}}$ , the rejection rate, not by the sticker price of one generation call, which is why validation pipelines rather than generation prompts are where most of the engineering effort in these projects actually goes.