Where am I going wrong on the following formula?

Bosch has a formula stating...

Lambda = (Xo2 / 3 + 1) / ( 1 - 4.76 * X02)

Then they show the following as references....

IP = 1.40
Xo2 = 12.0
Lambda = 2.42

This does not work given the above formula using 12.0% Xo2 or I'm doing Math Wrong.

Lambda = (Xo2 / 3 + 1) / ( 1 - 4.76 * Xo2)

Xo2 = 12.0
(12.0 / 3) + 1 = 5
1 - (4.76 * 12) = -56.12
5 / -56.12 = -0.089

Where am I going wrong?