Actually I should have checked my acct before posting!
It seems that I have got the "allstores" credit which is why I got the $10 - except on the receipt it say congrats $10 off shop. But upon logging into my acct it says I have $10 and then says "which will converted to 870 qff on 15/12/16
Confusing much!
It seems the 1600 is my current balance - minus the $10... of dear! even more confusing to say it like that.