Input defaults in workflow_call

Im trying to move some of my jobs into reusable workflows and preserve the current behaviour.
When using default values in inputs, are these in context of the caller?

Example:

on: pull_request_target
jobs:
    job:
        runs-on: ubuntu-latest
        steps:
            - uses: <org>/<project>/workflows/workflow.yaml@main

Reusable:

on: 
    workflow_call:
        inputs:
            pull-request-num:
                required: false
                default: ${{ github.event.number }}
jobs:
    job:
        runs-on: ubuntu-latest
        steps:
           # is thisthe pull request number from the on_pull_request_target event?
            - run: echo ${{ inputs.pull-request-num }}

will the default value for github.event.number be in “this” context, or the context of the caller workflow?

I have a monorepo with a lot of apps and libs that will only call certain reusable workflows from pull-request events only.

One reason for using defaults here is to prevent the “caller” workflow to pass an unwantet pull-request number. When working with pull-request-target I have to be careful to give any attacker any surface to work with. I can also make if-checks etc in the calling workflow, but then I have to maintain over 20 workflows for vulnerabilities in stead of only 1.