Welcome to the forum @chaozding
Suggest you have a read through the new guides, specifically the section on decimals:
Tokens guide (work in progress update from: https://docs.openzeppelin.org/v2.3.0/tokens)
You created 100,000,000,000 of the smallest unit of your token which at two decimals (two decimal places) is equal to 1,000,000,000.00 CZDT. Etherscan is displaying the number of tokens and not the smallest unit.
This is similar to dollars, which has decimals of two and the smallest unit is cents.
100,000,000,000 cents = $1,000,000,000.00. The number of dollars is displayed.
Regards the quantity of your tokens, it really depends on what the purpose of the token is. I would also consider using an ERC777 token (see OpenZeppelin 2.3).
Please ask as many questions as you need. It might be worth starting a new topic.
Also when you have a moment, it would be great to tell the community what you are working on