You cannot display auto numbers and calculated attributes offline. Refer to the following link for more details on this: https://docs.mendix.com/refguide7/offline
Check 4.6 Autonumbers and Calculated Attributes
I get the same problem,
At your training doc: https://gettingstarted.mendixcloud.com/link/module/123/lecture/1080
this usage will have problem with the error message.