Benchmarking is a way to separate calls by a specific metric such as call length.
Unlike Universal Analytics (UA) which would send the parameters to a different Event or Goal. Benchmarking parameters in GA4 will only send the parameters setup under the Benchmarking section.
An example below is setup to send a conversion every time a call is greater than or equal to 15 seconds. The parameters it will send to GA4 are action, category, and label. (other fields can be used depending on what you would like to see, including custom parameters.