If you are using Ben's kit, or the Taylor 2006, or the Leslies FAS-DPD, re-run the FC and CC tests using the 25ml line and counting drops as .2ppm, not .5. If your CC is less than .5, don't worry about it and go swimming. Remember: you don't know if it's .1, .3, or .5 for your CC--it's just .5 or less, but more than 0.

If it is .5 of cc:

Add bleach to shock up to 15ppm FC, see if CC disappears. If it doesn't, it's not a big deal, go swimming. I don't think it will matter since your FC is 8.5 with a CYA of 30.