Which parts of the job do you set up?

Choose the software your code needs and the time it may run. Modal Sandbox supplies the environment. If the job needs a browser, choose and configure that tool separately. For your first run, use a small fictional file and leave real accounts and shared folders out.

What affects the bill and what should survive?

Modal charges for requested CPU and memory over the sandbox’s lifetime, including time they are idle. Check the resources and timeout you set. If you use persistent storage, choose a separate test location and verify what writes are saved there. Keep the approved report and its inputs separately if you need to reproduce it.

What would you keep from a fictional image-size report?

Sketch a run that reads two invented image sizes and produces a small table.

Choose a time limit
Mark when the run should end and which resources it needs.
Separate temporary files and output
Name the one approved table you would keep and what can disappear at the end.