Made HOWTO a tiny bit better.

Documentation/HOWTO-change-firmware-and-compile-it_MeesElectronics.md

@@ -293,6 +293,8 @@ if (model == MODEL_A1) radio->setTxPower(txp, PA_OUTPUT_PA_BOOST_PIN);
     if (model == MODEL_A4) radio->setTxPower(txp, PA_OUTPUT_PA_BOOST_PIN);
 ```
 
+The `MODEL_A4` is an 8 bit value read from the EEPROM. This is the value we will write to the EEPROM later in this document with the command `rnodeconf /dev/ttyACM0 -r --platform ESP32 --model a4 --product f0 --hwrev 3`. The model number a4 is chosen from a list published in the file [https://git.meezenest.nl/marcel/RNode_Firmware_CE/src/branch/master/Documentation/BUILDING.md](https://git.meezenest.nl/marcel/RNode_Firmware_CE/src/branch/master/Documentation/BUILDING.md). It is shared with another board and it is probably better to choose a unique value. But it could be that Reticulum uses this value and maybe choosing a new number breaks Reticulum. Further research is needed. But for now let's use a4, because it works.
+
 ### Display.h
 
 The file **display.h** also has a board specific definition section. If the new board has a display, make sure there is a proper entry for it.  Our example board doesn't have a display, so we don't have to change this file. If your board has a display, make sure you make the proper changes.
@@ -323,7 +325,7 @@ This first time you flash a new board, this command will end with the error `Thi
 
     $ rnodeconf /dev/ttyACM0 -r --platform ESP32 --model a4 --product f0 --hwrev 3
 
-### Migrating to a other system
+### Migrating to another system
 
 When the rnode is flashed, it is signed with a key. If you connect the RNode to another system, this key cannot be validated. It is possible to write a new key to the RNode by erasing the eeprom and writing the local key to it.