Thank you very much for all the advice.

It is too late. I already add in all the expensive stuff from the store. Since I am going on vacation tomorrow, I wish to get rip of the algae before I leave. I did not know that I do not have to adjust the other stuff before I put in the shock.

Right after I put in the shock, I saw algae floating from the bottom of the pool.

The test result from Aquachek test kit is as follows:

FC 10 (probably more than that. I will try to dilute the pool water with same amount of water and test it again)

pH 7.2
Total Alkalinity 120
CYA 0-30

The problem is that I will be away for 6 days and starting tonight until tomorrow there will be isolated thunderstorms. I wish to close the pool cover so that no more rain water get into the pool. I cannot add more shock to keep the chlorine level up for a few days. Should I take the risk to put in one more time of shock tonight and not cover the pool until I leave tomorrow?