我应该为heroku设置哪个app键？

I am trying to deploy my laravel project on Heroku. In the deployment steps at https://devcenter.heroku.com/articles/getting-started-with-laravel , I am asked to set the 32 char APP KEY for the application

I am really confused, that should I use the already generated APP_KEY environment variable in the .env file which is something like this: APP_KEY=base64:3784jZeQ333utc4G8NxL9o2v6r8ct4ffTrRzFsStHrm0=

But this string is not 32 chars long, and the example in the steps clearly shows a random 32 char string. My env app key seems to be encryted.

I already tried using this env app key, but after deploying I get error: Whoops something went wrong.

-Should I have to use the SAME key as generated in .env file ?

I re-deployed my application again and used the entire base64 string of the .env file APP_KEY environment variable. It works fine now.