Function void Plugin:OpenScript(Instance script, int lineNumber = 0) [PluginSecurity]
If you want to open the 3rd line in a script, you have to use 2 as lineNumber.
This is a bit weird since Lua starts at 1, not 0.
The script editor also starts at 1, not 0.
And to finish it: The error stacktraces also start at 1, not 0.