With a CYA level of 60ppm, then your shock level would be 20ppm. So, don't add any more chlorine tonight. Test again in the morning within an hour or so of sunrise. You don't have to retest everything, just test FC and CC. Report how much loss you had (FC) overnight. If you lose more than 1ppm of chlorine OR if you have greater than 0.5ppm of CC, then you need to raise the chlorine back up to shock level in the morning.

In case you haven't yet seen it, here is our Best Guess Chlorine Chart that shows the connection between CYA and chlorine levels:
http://pool9.net/cl-cya/