I got feedback about experimenting, and I'm unsure how to process it.

I don't think you need to process it urgently, but I heavily recommend familiarizing yourself with it in the next 3 months before PSC starts. If you can run a few experiments end-to-end by then (come up with goal metrics, set up the experiment, launch it, analyze the data, and probably write a nice Workplace post about it), that would be great.

Experimentation is part of the lifeblood of Meta (this is what you get in a company that's both so big and so metrics-driven), so it's effectively a requirement to understand for almost all software engineers there. Being very skilled at it is very necessary going from E4 -> E5 in most orgs.

That being said, the experimentation infra at Meta is so, so complicated. I really don't recommend trying to understand on your own by playing around with things and reading the documentation - Even at Meta's current scale, it evolves too fast that the documentation/resources can't really catch up. I heavily recommend just having a 30-45 minute meeting with a tenured engineer on your team where they just explain all of Meta's experimentation concepts to you - That's how I learned to run experiments at Meta. Before this meeting, come up with a good set of questions to ask. To help you out, here's some questions you can potentially use:

1. How does our team use Deltoid and Scuba? Which is more important?
2. How do we use gatekeepers, quick experiments, and launchers?
3. What is a universe experiment?
4. What's the point of a holdout group?
5. What's a backtest?

And with each of these questions, you can ask for an example (ideally from your team's past) as well.