You probably will ask this question when configuring your vehicle profile, and selecting which OBD-II channels should be recorded. All of the recorded OBD-II channels share a common bandwidth, which means the less channels being recorded, the better the update rate is for a single channel.
In RaceChrono, there is a concept of “Fast channels” and “Slow channels”. The available bandwidth is divided equally between the fast channels, but the slow channels will always get only a small fraction of the bandwidth.
You should select any slow changing low priority channel as a “Slow channel”, for example most temperature channels. Anything else you should select as “Fast channel”, for example and especially, RPM, Speed, accelerator position etc. To maintain useful update rate for the recorded channels, make sure to select only the fast channels that you really need.