With a TC of 10 and FC of 7.9, then your CC should be 2.1, which means you need to bring your chlorine up to "shock" level, which with a CYA level of between 90-100 would be 20-25ppm according to Ben's Best Guess Chart. This should bring your FC & TC into balance and your CC down to 0 (or at least down to less than .5, which is acceptable according to most of the "gurus" on the board).