AEM 30-0300 lambda readings

I am having my vehicle tuned remotely. I recently purchased an AEM wideband. On the scanner I have readings above 2 lambda. My tuner says he has never seen that happen and he thinks something is wrong with the sensor. To my understanding the sensor can only read up to 2 lambda. When the gauge displays ?- - - -? it will say 9.99 in the scanner but in between it doing so it will have readings around 5 and 6 intermittently. These reading only occur during fuel cut off on deceleration. Does anyone have a similar experience or is my WB no good?