How would you have worked this out?

Convict224

I've recently started a new job, £20k pro rata, two days per week. I've just got my October pay, my first month and queried it with my manager. She has computed it completely differently to me. She was misinformed that I had worked only 7 out of the 9 available days when I had actually worked 8, so we both agree that I am owed 1 day's pay. But I still don't agree with what she paid me.
I don't want to give the numbers out and influence anyone, but would you mind working out what you think I should have got?

Convict224

Thank you Mick.That's exactly what I worked it out to. She worked it out as £494.63, but admits to owing me a further day's pay. Instead of paying me for the days I worked, she is deducting the days I didn't, if you see what I mean. I still think she has computed it wrong.