Settings for ExtraCPUs

I recently came across a need for the extracpus in Tweak Settings, never had to use it in 10+ years of cPanel use.

This one VPS I have has 3 available E5620 processors @ 2.40GHz, all quad core. The server is seeing high CPU loads recently & now wondering about the setting.

How is extracpus helpful? Do I account for the 12 cores available in the settings? Is it only for stats & logging, as a "feel good" setting? Just looking for a better explaination & wondering if it helps stave off a crash so I can kill processes to avoid a bad situation.

Thanks much
Karl