647l is last years tax code as your personal allowance was 6500 of paye tax meaning anything yhou make for last year 6500 of it is tax free
this year as part of the government initiative to help people into work they have raised the threshold to 7500 thus tax code 747l however i think you pay 40% tax on 35000 now instead of 37000
use this calculator if you are unsure of how much you have been taxed
http://listentotaxman.com/
if you have been taxed too much then contact hmrc in august and ask for a refund