The Reactor Lab material on the stoichiometry of multiple reactions is not consistent with the text, CD-ROM or web (www.SimzLab.com) and you may want to omit that portion of the Reactor Laboratory exercises.
Official ReactorLab website: you can download the latest version and/or more modules
Please check your CD-ROM that came with your reaction engineering book.
Latest version of ReactorLab at the time the CD-ROM was made is bundled with it.