I mean:

-> e.g. you ordered and payed for a Saturn on 20th June
-> Now you upgrade to Jupiter lets say on 10th August - you also do your "upgrade" payment on 10th August

What is the "paying" date for your order? 20th June oder 10th August? As far as I understood this will have big impact on delivery date of your machine due KnC said "First paid, first serve".