Some questions about the ATC command, please help me!

Hello everyone, I have encountered some difficulties when using ATC.
1. about the command: fix_modify AtC mesh create_faceset <id> plane <x|y|z> <val1> <x|y|z> <lval2> <uval2> [units]
      what does <val1> <lval2> <uval2> mean? How can I define a plane with these three numbers.I don't quite understand the instructions in the doc.

2. The input file for ATC in the lammps example contains the following parameters 
     thermo_style custom step cpu pe etotal temp f_AtC[1] f_AtC[2] f_AtC[3] f_AtC[4]
what does f_AtC[1] f_AtC[2] f_AtC[3] f_AtC[4] mean? I checked the documentation but did not find the relevant instructions.

3. about the command:
   fix_modify AtC  source temperature  spot 3612
   fix_modify AtC  source electron_temperature  spot 3612
   I think, these two commands add the same heat source for lattice and electron, and the system should be the same after balancing. But, I get the system temperature 344K for the first command, and 4000K for the second. Where am I wrong? the input code below:

You should ask the USER-ATC package authors. Their contact info
is in src/USER-ATC/README.