That is the Minecraft version, you need to know the Forge version.
Twitch puts its Minecraft files in Documents\Curse\Minecraft\
You have to make sure you add the exact text "logging":{}, the rest of it is trying to explain how to add that line while keeping the file readable to the launcher, easiest way is to find the end of the file where the last } is and put "logging":{} on the line just above and putting a comma on the end of the line just above THAT.
Unfortunately there is a reason I say to close Twitch and keep it closed through these tasks, if Twitch is running and you try to launch the pack through it it will reset the file we are changing, and it will reset it to Twitch's version of the file which breaks Forge's logging.
That's me trying to explain what the script does and how to use it, essentially it launches the Mojang Launcher the same way Twitch does, but my script doesn't reset the file we changed like Twitch would.
To use it just save it to your computer and in your twitch files find minecraft.exe and put my script next to it, then double click my script.