Ok - so on the Mr Porter purchase, if we take VAT off the 40 GBP, it makes sense. But 9 avios x 33 = 297 avios, not 200. So what is happening there?
And with Marriott, 107 x 5 avios = 535 avios. So what happened there?
So Marriott
Price £108, minus VAT (0.8 x 108) = £86.4
86.4 x 5 = 432.
No problem here.