I'm trying to trigger about 6000 processes from Process Builder (scheduled action) depending on whether it's x many days from a due date. After triggering the 6000 through the API, I noticed I can only see 1000 through Paused and Waiting Interviews (hopefully they rest are there somewhere). I also noticed some records which should have triggered a flow not having been triggered (task wasn't created). Honestly confused here! Thanks in advance.
You can have up to 50,000 flows waiting at any given time. Of those, up to 1,000 will be processed per hour. The list only shows 1,000 items, but the remainder should still be waiting. It will take a few hours for them to process. You can read more in Limitations for Waiting Flows.