At least you will understand about the delay and at least you are aware of the transaction withdrawal time that you can prepare ahead when you want to withdraw. I don't know either the process, it will probably manually checking about the withdrawal and they make sure it is the right transaction. As I said, you should not be in a hurry if you want to withdraw your fund on the site. However, you are free to consult the site about your withdrawal transaction if it is too much delay, reaching them would be not a problem, their staff is so friendly.
It is usually automatically checked on the first part, then only if a certain threshold is reached it becomes a manual one. They are not manually checking every 10 dollar withdrawal, at least it was like that when I worked in another casino, I was in marketing but we were all talking about since these type of complains hurts the marketing side as well, I had to talk with the people.
Small amounts are automatically checked and unless there is a double spend deposit or something then it ends up being fine. However after a certain amount, the question becomes how credible that person is, an account that had 100+ deposits totally 100 bitcoins over course of few years suddenly wants to withdraw 0.1 bitcoins? That is a lot of money but the dude is trustworthy so it goes pass right away.
A new person who deposited 0.1 and wants to take out 0.15 just 10 minutes later? Well they will take their time to see what happened there.