Contracts are sometimes very hard to understand. Basically, in a written contract, problems arises from those which are actually not specified on the contract itself.
There is a saying that "what you don't know won't hurt you" but it is not true.
Bear in mind that a contract not only binds you with the company. The company is also binded to you. Both ways, you should pay your obligations to each other as per the contract.
The point is, whatever is written in the contract should be followed.
If you haven't used your previous tickets, I am afraid you cannot retreive it anymore, usually that is a case, but in some instances, there might be an exception.
For a more fair and justified advice, I think you should coordinate with the LABOR OFFICE.