What learnings am I supposed to get when working on a task in a large codebase?

I’m currently an E4 at Meta, and this is my first big tech job. I recently had the opportunity to work on a front-end task for the first time here. The task was basically to add a new parameter to a bar chart on a certain page (for an internal tool). I’ve done front-end work before, but this was my first exposure to front end work at Meta.

I was able to complete the task by following how other parameters were added and copying the structure. But it left me with a bigger question that I’ve been thinking about :

> When I make a small change to the codebase, like adding a conditional value or a new chart parameter, how deep should my understanding go? What exactly should I aim to understand when working in a large codebase?

Should I understand how the file is rendered?

Should I trace the flow of data end-to-end?

Should I just focus on the part I’m touching?

How do I know how much is "enough" to learn from one task?

I’m trying to ramp up effectively and take the most learnings from every task I do. I don't want to just complete them without understanding. I’ve noticed that most of the time it's possible to do the work without really understanding what’s going on, but that will not help me grow into a senior engineer over time.

So my real question is: How do I take a more senior approach to tasks, even small ones? What should I be learning or looking for when I complete something? And how do I make the most out of the support I get from the senior engineer I’m working with?