I really don't understand your logic. It's not about having a nice number. Do u think AMD will ignore hundreds of millions of sales from the range you propsed in a financial report to have a nice number?
The way I look at it is the + sign is a very close number to reported number. So at minimum it would be 151m and max would be 154m, otherwise, they could say 155m+.
Besed on max number, xbox sold to consumer would be estimated around 41-42 Million's.