Reprimand with a probation of 1 year

I am working for a BPO company here in Makati.
I'm handling a payroll account for US clients.
I made an erroneous entry for one US client and was given by my supervisor a written reprimand on OCT 2011. Then I made the same mistake again in August 2012 and was given a Final written reprimand. I made another mistake last January 2013 and was now subject for hearing for termination. I was informed that the error that I made have a probation for a year.I was given a chance to explain myself for every occassion.
When I made a mistake by Aug 2012, my mistake on 2011 of October was "refreshed" and carried over for my mistake in 2013.is that okay?

you were only reprimanded and put on probation?? you were lucky you were not terminated.

habituality seems to be proven, but are the errors gross in nature? what were your mistakes? these 3 errors are what percentage of the total no. of entries you handle?

It's called payroll entry wherein I entered the wrong salary amount for an employee in the US. I'm actually thinking about whether there is any law that would prohibit a company in providing a reprimand that last for a year which I think is not good for the welfare of an employee. But thinking about Article 282 section A, which is about company policy, I think my reasoning would be invalid.