The ancestry report uses 'Ahnentafel' numbering. This means that the numbers for a person's parents will be twice as large as that person's number. For example, if a woman's number is 15, her father will be number 30, and her mother will be 31. Her child will be number 7.
This web site produced 2005 by Günther Fuhrmann, using the programm PAF 4