Interest on credit cards- newbie question

[sparks_E39]

I may need for the first time to have to use my credit card in the next couple of weeks, how much interest should I expect to pay on a £500 purchase at 16.9% apr variable if its not going to be paid back for about 6-8 weeks? I have no idea how this works having never used my credit card, had a loan etc etc (it exists for emergencies, I'd rather not use it but I don't have much choice) Ive been told that on a £1000 purchase at those rates I'd be charged around £10 per month if I paid back £50 a month, sound about right?

[sparks_E39]

Good news, I don't have to use it in all likeliness now, but thanks for the answers, all very helpful