Rewards Tier Ranking

I have a question regarding the degrading percentages on the VIP Rewards. How does it work? I needed $15 to my next rank. I waited a few days so I could buy Duke Nukem 3D at $20. When I checked my rewards first, it then said I needed $55 to next rank.
I get on now, and it says I'm 64%. How do I go from 90% to 64% in a week!? I thought it was based on the money spent to go from tier to tier. This feels like a huge rip-off for people to keep taking away what they've spent. I wasn't fully aware that pre-orders
(Digitals) didn't count towards the Rankings. I spent $250 on pre-orders just to have it not count (I have NO idea why that even is.) I was just curious how it works and why take away percentages from people spending money to rank.

:)

 

forza horizon 3 club tier rewards

i don't recieve rewards from tier,i'm tier platinum club

 

Tier rewards

Where are my loyalty reward cars in fh3??? I got my credit rewards from the hub and redeemed them. I've also unlocked and opened the second festival site. However I've never received my loyalty cars yet. Where are they??