How to know which fields in activity.info are populated?

I am new to this and working on a data field.  The info structure provides lots of information based on the documentation,  however when I run things in the simulator a lot of the fields are either null or 0.0  is there some documentation which would tell me which fields are actually populated when running on a specific device such as an edge 830?  Does one have to test it on an actual device to find out?