He can tell you - they're in his book !

If the vehicle details have been put into the machine correctly and the only
thing that matters here is the year of the vehicle  because when doing a BET
test the limits are the same for all makes i.e 0.30max for C.O - H.C should
be as low as possible such as 20ppm and the Lambda reading should be as
close to 1 as possible i.e 1.005 or 0.998 for example - the CAT tester only
see`s black or white i.e pass or fail - it is out of the testers hands.
If all that is out of range is the lambda reading this could be as simple as
a poor connection on the sensor and could be rectified by unplugging and
plugging back in a couple of times or a slight exhaust blow either before or
after the sensor could be to blame !
Hope this helps!!