Lots of algae, 0.5 CC

[zoffPool]

I was away for a week and now have lots of algae at the bottom of the pool. The question is with all the algae why is the Combined Chlorine level .5?

FC= 7, CYA=50, pH=7.5. TA=110

PS. The reason the FC is 7 (i think) is because I asked my wife to add chlorine tabs mid-week, And I suspect the tabs were added too late.