Bold letter C in DRF pp.s?
 

What does this mean/ I see this to the right of the track, distance and surface and before the split times

Some are within circles, some are not

I see the letter S sometimes, also

S means the pace favored speed with a soft pace, with a circle it means it heavily favored speed horses. C means pace flow favored closers, with a circle it heavily favored closers.