Philo was referring to point blank range (likely against a large wall), not maximum. PBR refers to the maximum range of a projectile when flying it flat with no adjustment for range. A rifle may have a PBR of 250 meters against 12 inch target, but that is far from its maximum range.
The lowest ranges I have seen for ballista was ~400 meters, but these were for the earlier machines (outswingers), not inswingers. Calculations based on a more modern hatra style ballista:
https://cyberleninka.ru/article/n/me...-roman-legions, produce a range of 786 meters with a 21.8 kg stone ball @ 118 m/s, resulting in an energy of 151 kj, or nearly ten times that of the warwick trebuchet. With a lead ball @ 45 degrees, range would exceed 1,200 meters w/ air resistance. Seems incredible, but reconstructions of torsion catapults confirm the performance: