It means your CTC is 95.05%. You need to gain 7.35% CTC to hit the cap. The easiest/simplest way to increase your CTC is by using mastery rating because it scales linearly (1 mastery rating is worth just as much at 1% CTC as it is at 95% CTC). Thus gaining 878 mastery rating would put you at the CTC cap. When you are above the CTC cap then the numbers will turn positive. I admit it isn't as clear as it could be.
Did you remember to activate raid buffs? You should always check your Combat Table Coverage when raid buffed, and the spreadsheet allows you to do so without begging random DKs, warriors or shamans to give you Battle Shout every 3 minutes, or spending money on eating buff food.