You can calculate it here:http://www.nhi.gov.tw/English/webdata/w ... ta_id=3153
Most people here will be class 1, "Employees of publicly or privately owned enterprises or institutions" or "Private school teachers". In the former case the employer pays 60% (I couldn't remember when I posted above if it was 60 or 70) while in the latter it's 35%. In both cases the employee pays 30%.
If you're only paying 330NT you're being counted as a Bracket 1 employee (monthly income level below NT$22,800), which should mean you only pay 270NT per month. The additional 60NT would normally be a "supplementary premium". If I recall correctly this is basically the difference between your actual salary and the minimum salary in your wage bracket, multiplied by 0.02. In my experience the sum of this and the wage bracket rate will take you to around 6%, give or take a bit (unless you're earning significantly higher than the bracket ten wages, which will obviously skew the numbers quite a bit).