newbie - production vs development

I'm having issues with running codeigniter in development mode.
I have changed the env file to development mode
#--------------------------------------------------------------------
# ENVIRONMENT
#--------------------------------------------------------------------

CI_ENVIRONMENT = development

I then run the spark test server:
michael@michael-Aspire-F5-572:~/Programming/Codeigniter/framework-4.3.6/codeigniter4.3.6$ ./spark serve

CodeIgniter v4.3.6 Command Line Tool - Server Time: 2023-07-10 06:07:34 UTC+00:00

CodeIgniter development server started on http://localhost:8080
Press Control-C to stop.
[Mon Jul 10 16:07:34 2023] Failed to listen on localhost:8080 (reason: Address already in use)
CodeIgniter development server started on http://localhost:8081
Press Control-C to stop.
[Mon Jul 10 16:07:35 2023] PHP 7.4.3-4ubuntu2.19 Development Server (http://localhost:8081) started

However when i go to http://localhost:8081 in my browser, it indicates it is in production mode?? 
What else do I need to check?
thanks
m