It would be nice to clarify that the directory referenced are 2 levels under the home directory and maybe instruct to already create path and file for mock.py script like so:

In the next steps we will write in total 3 files (seat-application.json, mockservice.json, mock.py) inside 2 important directories: /data/var/containers/manifest/ and /data/var/mock .
Before continuing with this guide, make sure to be in the right directory, run:

cd ~/../..

If you want, you can already create the mock directories that will constitute the python script to run mockservice:

mkdir ~/../../data/var/mock/
touch ~/../../data/var/mock/mock.py

If you don't, you will be reminded later.