There is no predetermined number of Lictors that a Strategoi may have active at one time and not all of them act in this capacity openly. They are the troubleshooters for the Ventrue clan, each with their own distinct specializations, trained to resolve a particular type of problem (martial, diplomacy, financial, Masquerade, etc.).
Since the Strategoi seldom get their hands dirty, they send these individuals out to address problems, enforce policy and procedure, and to administer judgment. Lictors are the eyes and ears for the Strategoi, reporting directly back to them about the various domains and directorate that they visit.
These are the strong-arm of the Ephorate, possibly best thought of as the clan's internal police force. A Ventrue of any significant standing can call upon their Strategos for assistance, and a single Lictor is often what they send in response. The Strategoi usually pick relatively young up-and-coming Ventrue to elevate to this coveted role, as this position often serves as a fast track (though certainly through a “Trial by Fire”) to the upper echelons of the clan.
Many Ventrue referred to Lictors as judge, jury, and oftentimes executioner for the clan.