I remember going through this a few years back.
They take into account how much you make 2 years prior, so if you are a new student with no income, you can apply for premium assistance based on your last years income tax (ie. 2015 right now).
They are able to back date 6 months I believe, so if you do your income tax in jan/feb for 2016 showing a significant reduction in wages in 2015, you can minimize how much you have to pay for MSP. https://extranet.gov.bc.ca/forms/gov/health/msppa.html
Use that to help calculate and I find calling the number more helpful than emails/letters and shit...but can take a lot of time to get through.