When Supplier is Greek, the Invoice Id third segment must be a positive integer
/ubl-invoice:Invoice/cbc:ID[$isGreekSender] | /ubl-creditnote:CreditNote/cbc:ID[$isGreekSender]
string-length(normalize-space($IdSegments[3]))>0 and string(number($IdSegments[3])) != 'NaN' and xs:integer($IdSegments[3]) >= 0