First off, welcome to the Pipedream community. Happy to have you!
Let me try to explain, both sources and workflows count toward your invocations.
On your Telegram workflow for example, you ave a Telegram DM Source that listens for new DMs and emits events to subscribing workflows.
When a new DM is detected, the source is triggered and this counts as an invocation. Then the workflow is triggered from this new event and that also counts as an invocation.
One of the ways you can optimize on invocations is to have one source power more than one workflow. This will help save you on invocation costs.
Here’s the full definition of an invocation in our docs that explains this: