Values OBD2

Good morning, my appointment is as follows. I have a universal HUD by OBD2 that indicates several values, Speed, Rpm, Battery charge and instantaneous consumption among other things. RD gives calculated values ​​and I would like to use the value by OBD2, but I am not able to find it. Any ideas?
P.S. surely it is nonsense and I am very clumsy! Thank you!

The Speed, RPM and Battery voltage come ‘as is’ from OBD2, so there is no calculation there. The instant fuel consumption is calculated by RealDash, as there is no standard PID to read this value from. This means that every vehicle has their own command to read this information. Because of this, RealDash attempts to calculate the fuel consumption from other data sources by default.

It is possible to read the instant fuel cons. from your vehicle, but you would need to know what command is required to read this info. Unfortunately we do not have extensive database of these commands.