If a quantity is not stated it means 9 or more, something of an Amadeus standard that. However there is still a bit of a risk since the buckets are dynamic, and there is a small risk that the system will recalculate after your booking. Since you can cancel reward seats without charge within 24 hours, you aren't going to lose anything by giving it a go. But if you would value some hand holding then I guess you can ring up and pay the Service Centre fee.