SOPP263: About pedal points

This question was sent by Ron. Hi Vidas, Do I have this right? Pedal point, as the vertical column of numbers below the chords, which can be 3s, 5s, 4s, 6s, 9s., flat whatevers to the root? Also, more than one, even two, three, four pedals held down at a time, sustained over the chords or measures? So, a 4 below a 6 in CM would be the F and A pedals, held down? A 5 and a flat 9 (flat 2nd an octave lower) would be G and D flat, maybe held down under some other dissonant chord like fourth degree (F) chord? Is my terminology correct? Thanks!