189 visa employment proof: Discrepancy between job start date and date on contract

[RubyMonday]

Currently completing my application for a 189 visa and am confused on what to put as my start date and whether to include my employment contract or not. 

So I started work with the NHS on the 12th September 2016 and was a registered nurse with the NMC from that date (which I have supplied a statement of entry to prove). To cover me from the 12th (while the NHS processed my nursing registration) I was given a job contract as a nursing assistant but worked as a registered nurse. The registration took two weeks to process so when I was given the new contract for the staff nurse it was dated 1st October. I have a work reference which includes the 12th as my start date, I had used this for the skills assessment so the 12th is included on their outcome letter.

If I give the 12th as my start date when applying for the visa then it matches the skills assessment, nursing registration and job reference but not the employment contract. If I give the 1st October then it matches the employment contract but not the others. Without the employment contract I have as proof: Every third payslip, Nursing registration/statement of entry and the job reference. I also have the original conditional job offer subject to health, criminal records checks etc I could include. That confirms the offer of employment as a registered nurse and was issued in July 2016 but doesn't include the start date. 

I've only worked for the one employer since I finished university in September 2016. I'm claiming points for 5 - 8 years work experience and have provided payslips for over 6 years from October 2016 through to this year so those two weeks make no difference in terms of points.

Should I include the employment contract or not? I'm just concerned that they might see the discrepancy as false/inaccurate information.