relocation payback question

What is the name of your state? indiana company is in nebraska

I just relocated to indiana to work for a division of a company in indiana when they decide to close it down and bring it in house to nebraska. we were offered a position and relocation. we signed in April and were to move in august. we recieved $20,000. if we didn't accept the offer we would get $12,000 severence pay. I accepted but personal issues arose and I quit in august after accepting in April. The letter stated

*You must reimburse (xxxxxxx) a pro-rated amount if you voluntarily terminate your employment or are released for cause (to include, but not limited to negligence, performance or insubordination) prior to the completion of eighteen months of employment with (xxxxxxxx).

I've been with the company for a year total would I only have to pay a prorated of the six months left or would it start when I signed the letter and also who decides what the prorate would be it was never mentioned.

more info

I had been working for the company since 8/2/2005 I quit 8/23/2005


March 9, 2005


name


Dear ?
We value you as an employee and appreciate your dedication to(xxxxx). This letter is to outline the proposed offer of employment being extended to you.

Employee ID: xxx
Department: xxx
Work Location: xxxx
Supervisor: xxx
Job Title: xxxx
Work Hours: M-F, 8-5

Salary: xxxxx per month

Moving Allowance*: $20,000 allowance to be used for, but not limited to, sales commission on the sale of your existing home, closing costs, house hunting trip to xxxxx, temporary living expenses, mileage and the physical move of your household goods.

*You must reimburse xxxxxxx a pro-rated amount if you voluntarily terminate your employment or are released for cause (to include, but not limited to negligence, performance or insubordination) prior to the completion of eighteen months of employment with xxxxxx.

Start Date: 4/1/2005
Next Review Date: 8/2/05

Nothing in this letter may be construed as a contract or guarantee of employment for a definite period of time.

At the time you receive this offer letter, you will have 30 days to review and notify the Employment Center of any discrepancies. Please call the Employment Center at xxxxx


Signed

xxxxxxxxxx date: xxxxxxxxxxxxxx

Duplicate post

sorry didn't know where to post

Didn't know where this would fit in.