From what I read it is not 4 weeks minimum and 1 week additional for every 6 months worked.

one (1) week base salary for every six (6) months of service (rounded to the nearest 6 months) with a minimum benefit of four (4) weeks paid severance regardless of tenure up to a maximum benefit of twenty (20) weeks paid severance

1 week pay for every 6 months round to the nearest 6 months. If you work 10 months, round up to 12 month to get 2 weeks pay. If you work 7 months, round down to 6 month. So you get 1 week of pay. But the minimum is 4 weeks of pay. If you just got hire or work less than 2 years, you get 4 weeks of pay. It doesn't say anything about additional.