definition of absence in reference to maternity leave

I just came from a maternity leave. I went back to work on June 18, 2011. We are being paid semi-monthly, with a cut-off period of 9th-23rd and 24th-8th of each month. So this 30th of June, my salary is covering the cut-off of 9th-23rd of the month. My salary was computed as five days of work (18-22, 23rd being rest day) and nine days of absence. (9-17) We get paid P9, 000 semi-monthly. So my net pay for the 30th was just more than P1, 500.00. Our finance manager was insisting that their computation was correct because I was "absent" during the days I was on my ML. They said that SSS all ready paid me on those days, so they have to deduct those days against my salary. I need help on what to do. Was that even legal? Thanks!

were they days that you worked, but were not paid for?

In our company, you get paid with your basic pay divided by two, regardless of the days of work. Then if you were absent, you will just get deducted that absence. For our cut-off of 9th-23rd of the month, I went to work between 18-22, because 23rd is our team's rest day. On the 9th-17th, I wasn't required to go to work because I was still on maternity leave. Which means I wasn't really absent on the 9th-17th because I wasn't required to go to work. So why did they deduct nine days of absence from my pay? I had a net pay of P1, 500.00 + after working five days in a cut off. I work in a call center, so that doesn't seem right. My salary seemed like below minimum...

if you availed of the maternity leave benefit, then those days were already paid for.